* Convert render.js to typescript

* Compile tsx files too

* Remove internal renderErrorToHTML function

* Interopt component result

* requirePage doesn’t need async

* Move out enhancing logic into it’s own function

* Remove buildManifest from renderPage

* Move render into it’s own function

* Change let to const

* Move renderDocument into it’s own function

This link ref is no more necessary to include in the Head Section.  It cause error 404 in the console: http://localhost:3000/_next/static/style.css net::ERR_ABORTED 404 (Not Found)

This PR will

- allow nextjs export to use all available CPU cores for rendering & writing pages by using child_process
- make use of async-sema to allow each thread to concurrently write multiple paths
- show a fancy progress bar while processing pages (with non-TTY fallback for CI web consoles)

The performance gain for my MacBook with 4 CPU cores went from ~25 pages per second to ~75 pages per second. Beefy CI machines with lots of cores should profit even more.

* Update all dependencies and remove redundant ones from package.json. (60f9ee5)
* Fixes #5596 by adjusting nodemon scripts (d4b7d3a)
* Fixes `npm start` on windows by using `cross-env` (9555217)
* Move compiled server out from `.next`. Compiling other JS into `.next` seems incorrect. (79fce02, 
9ce7086)
* Partly fixes #5753 by making sure typescript compiles with `es2017` as target, at least ensuring code is runnable on node 8. Previously it was compiled with `esnext`. (9176e92)

--- 

I tried improving the structure by keeping source in `src/app` and `src/server` and then building to `dist/server` and `dist/app` but I didn't really get it to work and made most configs more complicated. Moved the built server out from `.next` anyway.

The `initialNow` prop is used to avoid content mismatches when Universal/SSR apps render date values using components like `<FormattedRelative>`.

If this value is created in `render()`, then the server will generate it and then the client will also generate it during hydration / initial render, resulting in two different values and content mismatches like:

> Warning: Text content did not match. Server: "in 1,741,545 seconds" Client: "in 1,741,543 seconds"

If the value is instead generated in `getInitialProps`, then the client's initial rendering will match because it will use the same value sent down by the server.

There were several issues with the example [examples/with-firebase-hosting-and-typescript](https://github.com/zeit/next.js/tree/canary/examples/with-firebase-hosting-and-typescript)
* `npm run serve`
  * Has no `pre` task that actually builds the app. Requires manual running of all build scripts.
  * Will choke on windows because trying to set environment variables with `NODE_ENV=production`
* Outdated Typescript and Tslint
* Not being able to deploy because `firebase-tools` being of a deprecated version.
* Structure, which I understand is based on `firebase-tools` generation, is confising with `src/functions/src` being generally bad structuring.

I remedied this and also improved some other factors:

* Remove dependency `prettier` as it is unused (f4d6f54)
* Upgrade all dependencies (09a9193)
  * Use upgraded firebase dependencies to deploy to node 8 environment (87e1e09, 7d8055b)
  * Remove deprecated tslint rule `no-unused-variable` (9392162)
* Flattened filestructure in `src/functions` (097a25a)
* Use ES import when importing next (6c99adb)
* Fixed incorrect name and added somewhat to the description in package.json.
  `with-firebase-hosting` → `with-firebase-hosting-and-typescript` (1ffa0b5)
* Fixed `serve` script by building before running, using [`cross-env`](https://www.npmjs.com/package/cross-env) to set environment variables and remove unecessary flag. (3a1e221, 422ccee, 8811e44)
* Add `.firebase` cache to `.gitignore` (4d7cbe4)
* Add `-C` (clean) flag when copying dependency files `copy-deps` (0826708)
* Use `strict: true` in the functions tsconfig (229b04f)

This was tested by running serve on windows and linx(WSL) and deploy on linux(WSL)

---

This is based on #5819 but correctly based from `canary`

* Upgrade React version

* Update size-limit test to account for React change

Hello! 
I was looking at the [`with-firebase-hosting`](/zeit/next.js/tree/canary/examples/with-firebase-hosting) example and was having some various issues running it:

* `npm run serve` will choke on windows because trying to set enviroment variables with `NODE_ENV=production`
* `npm run build-funcs` failing because of babeljs mismatches between `@babel/cli@^7.0.0-rc.1` and `next@^6.0.3`
* Not being able to deploy because `firebase-tools` being a deprecated version.

I remedied this and also improved some other factors:

* Use standard JSON formatting on `package.json` so that `npm install` doesn't cause changes on every run. (a83e930)
* Remove "prettier" as a devDependency as there is no use of it in the example and most other examples does not have it as a dependency. (6095663)
* Update all dependencies. The simple usecase in this example didn't really require any changes to the code. (ccde086)
  * [`firebase-admin@6`](https://github.com/firebase/firebase-admin-node/releases/tag/v6.0.0)
  * [`firebase-functions@2`](https://github.com/firebase/firebase-functions/releases/tag/v2.0.0) 
  * [`firebase-tools@4`](https://github.com/firebase/firebase-tools/releases/tag/v4.0.0)
  * [`firebase-tools@5`](https://github.com/firebase/firebase-tools/releases/tag/v5.0.0)
  * [`firebase-tools@6`](https://github.com/firebase/firebase-tools/releases/tag/v6.0.0)
* Make `npm run serve` runnable on windows using [`cross-env`](https://www.npmjs.com/package/cross-env). (b20dda7)
* Update `.gitignore` to ignore firebase cache (bf761b7)
* Remove `src/app/.babelrc` that seems to have been added as a previous bugfix but doesn't seem to do anything currently. (1b02045)
* Remove point from [`README.md`](https://github.com/zeit/next.js/blob/canary/examples/with-firebase-hosting/README.md) that was mentioning any `predeploy` hooks in `firebase.json` as they were removed in 4f4b7a1b. (5636d9f)
* Use the possibility added by upgrading `firebase-tools` to [`>=4.0.0`](https://github.com/firebase/firebase-tools/releases/tag/v4.0.0) and `firebase-functions` to [`>=2.0.0`](https://github.com/firebase/firebase-functions/releases/tag/v2.0.0) to make the deployable functions use node 8 rather than node 6. Also make babel compile with node 8 as target for less polyfills etc. (c954cc2)
  * Added comment to [`README.md`](https://github.com/zeit/next.js/blob/canary/examples/with-firebase-hosting/README.md) explaining how firebase deploys to node 8 and that babel will compile code for node 8. (d8b2e65, 91953dc)

This was tested to `serve` on windows, linux(WSL) and on mac. Deploy was tested on linux(WSL) and mac.

---

This PR is a based on #5806 with correct base.

---

🔔 @jthegedus @timneutkens 

Per @timneutkens suggestion [here](https://github.com/zeit/next.js/pull/5631#issuecomment-440588455) I went ahead and gave a shot at trying to document `renderPage` usage.

This PR:
- Documents `renderPage` legacy and current usage.

* Added a new example with relay modern and a graphql server with express.

* removed .graphqlconfig file from with-relay-modern-server-express example

* ADD with-firebase-hosting-and-docker example

* Improve doc

This PR Fixes #4920

So the problem is that when a next.js application is built on windows, the `pages-manifest.json` file is created with backslashes. If this built application is deployed to a linux hosting enviroment, the server will fail when trying to load the modules.

```
Error: Cannot find module '/user_code/next/server/bundles\pages\index.js
```

My simple solution is to modify the `pages-manifest.json` to always use linux separator (`/`), then also
modify `server/require.js` to, when requiring page, replace any separator (`\` or `/`) with current platform-specific file separator (`require('path').sep`).

The fix in `server/require.js` would be sufficient, but my opinion is that having some cross-platform consistency is nice.

This change was tested by bulding an application in windows and running it in linux and windows, aswell as building an application in linux and running it in linux and windows. The related tests was also run.
# Conflicts:
#	test/integration/production/test/index.test.js

The demo did not work. Updating to babel-plugin-inline-react-svg v1.0.1 did work.

Google seems to be deprecated the legacy realtime database and moving towards default use of Firestore, although it's still officially in beta. This PR migrates towards Firestore and the recommended loading methods for the Firebase 5.6.0 libraries. Note: the Firebase and Firebase-Admin dependencies should be updated to 5.6.0 and 6.3.0 respectively.

Hey @timneutkens I've updated this example a bit.

- Fixed `/asserts` spelling to `/assets`.
- Removed the `/assets/styles.less` as importing this caused the entire ant-design css sheet to be loaded, now only the React components imported will have their styles loaded via the babel plugin which was already configured. Resulted in dropping the CSS for this example from ~630kb to ~220kb.
- Removed `index.js` as it's not needed.

* Remove app variable as it’s only used once

* Remove double spread

* Move send-html function and rewrite in typescript

* Move getPageFiles and convert to ts

* Move getPageFiles and convert to ts (#5841)

* Move getPageFiles and convert to ts

# Conflicts:
#	packages/next-server/server/render.js

* Fix unit tests

* Move getPageFiles and convert to ts

# Conflicts:
#	packages/next-server/server/render.js

* Fix unit tests

* Added length calculation for insert of cache rather then default to 1. changed default cache from 100 to 100MB

* adjusted for lint

Couldn't find a reference to these functions as next-server uses the renderToHTML directly.

We don't have to check if the file already exists here, since it's always in production mode (dev overrides the readBuildId method to always be `development`) If the file is not found (error is thrown) we check if the file exists. If not we throw a helpful error. In other cases we throw the original error.

Firebase has some issues with grpc. ( Firebase has some issues with grpc ) This is resolved in a newer version of firebase. Especially with npm 6.4.1. https://github.com/firebase/firebase-js-sdk/issues/1341

Issue #5688

* Add tsc type checking

* Add linting on circle

* Add node-fetch types

* Use strict mode

We ran into this eg on hyper-site, which has `module.exports` in the content.