ci: add bot to remind users about docs builds if docs have changed

[henryiii]

@joerick, you might be interested. Have no idea if it actually works, based on the example here: https://github.com/actions/github-script#comment-on-an-issue .

[henryiii]

Honestly, just noticed the readthedocs line in the checks, maybe that's enough if there's a way to get to it from there.

[henryiii]

Yes. clicking details jumps to the build. Fine to just do that, I just didn't notice it in the list of checks. How did you set that up? Looks like it's here: https://docs.readthedocs.io/en/stable/guides/autobuild-docs-for-pull-requests.html

Hmmm, have to try that other places. :)

[henryiii]

Since there's a spot in the checks for it, and I've added it to my repos so I'm getting used to it, I think that's fine, and this is not needed.