* add new example

* update gitignore

* fix lint

* fix linting

* fix linting again

* update unstated example

* remove unsued var

* update readme

* Add docs for returning `null` from generateBuildId

* Add test for setting custom buildid

* Fix linting

* Delete .babelrc

* Update package.json

* Create next.config.js

* Update next.config.js

#5521

There were some strange quotes and misaligned html on the page in the `with-emotion` example.

* Add tests for isomorphic-unfetch bundling issue

* Remove unneeded extra option

* Remove isomorphic-fetch

Example deployment on now v2: https://nextjswith-mdxexample-r8b1vzjbn.now.sh

Same as https://github.com/zeit/ncc/pull/80

* Fix for locale.split is not a function.

Following from https://github.com/zeit/next.js/pull/5488

- Renamed languages to supportedLanguages
- Firstly, accept languages based on supportedLanguages
- And finally, accept a single language, if it returns false, the default of 'en' is used.

I looked at the navigator library, which is used by 'accept', this should be a more solid solution, since we can now know that `const locale` is always a string.

// Before (Sometimes returns an array as `const local`)
const locale = accept.language(languages) || 'en' 

// After (Always returns a string)
const locale = accept.language(accept.languages(supportedLanguages)) || 'en';

* Update server.js

Update variable name.

Fixes #3705
Fixes #4656

- No longer automatically dedupe certain tags. Only the ones we know are *never* going to be duplicate like charSet, title etc.
- Fix `key=""` behavior, making sure that if a unique key is provided tags are deduped based on that.

For example:

```jsx
<meta property='fb:pages' content='one'>
<meta property='fb:pages' content='two'>
```

Would currently cause

```jsx
<meta property='fb:pages' content='two'>
```

### After this change:

```jsx
<meta property='fb:pages' content='one'>
<meta property='fb:pages' content='two'>
```

Then if you use next/head multiple times / want to be able to override:

```jsx
<meta property='fb:pages' content='one' key="not-unique-key">
<meta property='fb:pages' content='two' key="not-unique-key">
```

Would cause:

```jsx
<meta property='fb:pages' content='two'>
```

As `key` gets deduped correctly after this PR, similar to how React itself works.

Slowly moving files over 💯 

Fixes #5778
Fixes #3650

* Fix polyfill for ie11

* Use esmodules only when using webpack

* replace all i18next related examples with the recommended next-i18next module

* update readme

Added next/babel in .babelrc
Upgraded babel-macros to babel-plugin-macros
Upgraded preval.macro

* Make sure const/async is transpiled

* Use babel common compilation instead

- Replaces taskr-babel with taskr-typescript for the `next` package
- Makes sure Node 8+ is used, no unneeded transpilation
- Compile Next.js client side files through babel the same way pages are
- Compile Next.js client side files to esmodules, not commonjs, so that tree shaking works.
- Move error-debug.js out of next-server as it's only used/require in development
- Drop ansi-html as dependency from next-server
- Make next/link esmodule (for tree-shaking)
- Make next/router esmodule (for tree-shaking)
- add typescript compilation to next-server
- Remove last remains of Flow
- Move hoist-non-react-statics to next, out of next-server
- Move htmlescape to next, out of next-server
- Remove runtime-corejs2 from next-server