* Implement circular JSON err.sh link
* Add test for getInitialProps returning circular json
* Make test warn less
* Fix tests
* Add reference to original tests
# Fixes https://github.com/zeit/next.js/issues/5674
This adds config option
```js
// next.config.js
module.exports = {
crossOrigin: 'anonymous'
}
```
This config option is defined in the webpack Define Plugin at build.
`Head` and `NextScript` now use the config option, if it's not explicitly set on the element.
This value is now passed to Webpack so it can add it to scripts that it loads.
The value is now used in `PageLoader` (on the client) so it can add it to the scripts and links that it loads.
Using `<Head crossOrigin>` or `<NextScript crossOrigin>` is now deprecated.
* 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
* Move __NEXT_DATA__ into a application/json script tag
As outlined by @dav-is here https://github.com/zeit/next.js/pull/4943
* Set __NEXT_DATA__ for backwards compatability
Clears the way a bit for #4943, also makes _document.js less complex, and will allow us to move `__NEXT_DATA__` to a `application/json` script tag.
Also this causes a slightly smaller bundle size 😌
