* Asynchronously check for type errors

* Add TODO

* Fix webpack invalidation

* Show TypeScript error in dev client

* Move client-side dev JS to dev folder

* Move eventsource polyfill

* Move source-map-support

* Move error boundary

* Deprecate Container in _app

* Make initialRender check better

* Remove unused code

* Only support one subscription as there is only one

* Don’t spread object

* Shorten property name

* Add container in development too

* Simplify query update logic

* Run prettier over packages/**/*.js

* Run prettier over packages/**/*.ts

* Run prettier over examples

* Remove tslint

* Run prettier over examples

* Run prettier over all markdown files

* Run prettier over json files

* Make sure to dismiss type error after being fixed

* Update test

Fixes: #5481

Upgrades `standard` to major version 12

Fixes #5363

I noticed this happening when making some changes on the nextjs.org/learn app. Basically we didn't apply updates when a warning was emitted from webpack. This would cause issues for users using eslint-loader or similar too.

- Implements Lerna
- Moves all source code into `packages/next`
- Keeps integration tests in the root directory

## Issue

Currently react-error-overlays launch-editor functionality doesn’t work because the module paths are in the wrong format.

## Todo

- [x] Keep source-maps enabled

## Related

https://github.com/zeit/next.js/pull/4979

This fixes intermittent `loading...` on some requests which surfaced on zeit.co when upgrading

This PR adds links to the [react-error-overlay](https://www.npmjs.com/package/react-error-overlay).
This allows a developer to open a stack trace in its own editor.

![codelinking](https://user-images.githubusercontent.com/1265681/44278860-a63e0a80-a24f-11e8-9c69-c5365c026c58.gif)

Closes #4813

Webpack 4, react-error-overlay, react-loadable (major)