Dogfooding Docusaurus 2

Created by: yangshun

Is this a bug report?

Hi there! Docusaurus team here! We're currently developing Docusaurus 2 and are almost done with an MVP that doesn't include translations and versioning features, which means there's feature parity with CRA's current usage of Docusaurus. We'd like to dogfood v2 on CRA mainly to try out the migration process with existing v1 sites.

Docusaurus 2 brings about many improvements:

Client-side rendering with prerendering (site works without JavaScript!)
More flexible appearance - Customizable layouts, CSS modules, etc
Embeddable interactive React components within markdown via MDX

Downsides:

Documentation for v2 isn't quite ready yet, but given that CRA is not using too many features of Docusaurus, that's probably ok.
We use CSS variables in v2 and hence IE11 isn't supported. We plan to support a way to build an IE11 compatible version which replaces CSS variables entirely with its values, but it won't be arriving that soon. Update 4/16/19: This is done.

Would the CRA team be open to dogfooding v2? We would do the initial migration and help out with any issues that arise. There aren't too many breaking changes. If you all are agreeable, we plan to kick off the process in May. Let me know what you guys think!

cc @endiliey @JoelMarcey