Document Read the Docs build pull requests

[paw-lu]

I was recently bitten by the sphinx incompatability with other documentation packages when it got bumped to 5.0. Similar to this repo:

• Bump sphinx from 4.5.0 to 5.0.1 in /docs #1216

But I didn't catch it on time—since all my testse passed—and merged it. I didn't know (until I looked at this repo and #1216) that Read the Docs can be configured to build docs based on PRs and check their success. Seems useful! Thanks!

Looked into it a bit, and I assume to get this check, you must enable preview Documentation from Pull Requests. I don't think this is mentioned in the Read the Docs section of the documenation. Would be nice to document it!

As always, would be glad to provide a PR!

[cauliyang]

I also meet the problem, bump sphnix to 5.0 will cause dependencies conflict. So I did not upgrade that 😑.