DOC: restore SHA to footer

[tacaswell]

PR Summary

Depends on matplotlib/mpl-sphinx-theme#54 being merged.

We used to include the exact commit used to build the docs in the footer (see https://matplotlib.org/3.4.3/index.html) however that got lost as part of the move to mpl-sphinx-theme. This adds the option to put this in the footer again.

[tacaswell]

This will also require a pin forward on the version of mpl-sphinx-theme we require to build the docs.

[QuLogic]

There is no pin on main, only the release branch.

[tacaswell]

[QuLogic]

With a small bit of CSS:

.bd-footer__inner {
	display: flex;
	flex-wrap: wrap;
}
.footer-item {
	margin: 0 0.5em;
}
.footer-item:first-child {
	width: 100%;
}

we can get it together like before:

which I'm not sure if that should end up in mpl-sphinx-theme?

[tacaswell]

I am in favor of leaving the CSS tweaking for later.

[jklymak]

Feel free to self-merge if mpl-sphinx-theme is already at 3.7

[tacaswell]

Feel free to self-merge if mpl-sphinx-theme is already at 3.7

it is in a funny state (due to branch protections I could not push the version bumping commit to main but I could push the tag, will fix that soon), but there is a release on pypi.

[tacaswell]

manually cancelled the appevyor to unblock it for other PRs.

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout v3.7.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 73909bcb408886a22e2b84581d6b9e6d9907c813

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #24781: DOC: restore SHA to footer'

4. Push to a named branch:

git push YOURFORK v3.7.x:auto-backport-of-pr-24781-on-v3.7.x

5. Create a PR against branch v3.7.x, I would have named this PR:

"Backport PR #24781 on branch v3.7.x (DOC: restore SHA to footer)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

[tacaswell]

Will backport this as part of #25194 .

[ksunden]

Backport included in 3.7.0 final preparation