Docusaurus: Document the ability to provide a custom layout

[JoelMarcey]

Is this a bug report?

No. See https://github.com/facebook/Docusaurus/pull/128 for implementation details.

Have you read the Contributing Guidelines on issues?

Yes

Environment

N/A

Steps to Reproduce

See https://github.com/facebook/Docusaurus/pull/128

Expected Behavior

N/A

Actual Behavior

N/A

Reproducible Demo

N/A

[FarooqAR]

Can I take this issue?

[JoelMarcey]

@FarooqAR Absolutely. Thank you very much! When you send the PR, we will review.

[FarooqAR]

@JoelMarcey Hasn't pr#763 already solved this issue?

[JoelMarcey]

Ah -- I didn't even see that PR. Sorry. I guess it has been taken.

If you have feedback on the PR, please let us know in the PR itself.

[endiliey]

Custom layout got removed because upon investigation it actually doesn't work :sob:

Let's leave custom layout on v2 implementation