Enable version warning banner

[stefanv]

Description:

#6896 tried to add a version warning banner.

This is now supported by the pydata-sphinx-theme directly: https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/announcements.html#version-warning-banners

• We should enable it. (Enable version warning banners for docs #7139)
• Also investigate if we can retroactively add it to older versions, even if that means statically ingesting it.

Way to reproduce:

No response

Version information:

No response

[lagru]

I think we have to wait a bit until this bug pydata/pydata-sphinx-theme#1450 is resolved...

[lucascolley]

It looks like the theme website itself has this working for older versions. We're going to try to do this in SciPy once we update our theme version (hopefully imminent).

EDIT: hmm, looks like they only have it working for 0.14.4

[lagru]

We're going to try to do this in SciPy once we update our theme version (hopefully imminent).

Maybe I'm dense, what will you try? Manual backporting or rebuilding the old docs?

[lucascolley]

Not sure exactly how yet, but we'll at least do it for current/future versions. One quote from scipy/scipy#19699:

maybe we could indeed get away with manually patching what's already out there (don't really like that, but far less work if it can be done with high degree of safety, and perhaps only last N releases but not too far back)

[stefanv]

Manual editing is probably easiest. We can add a static banner that points to /stable, or insert a piece of Javascript that renders from the dev docs. I think the static banner is fine, but the latter having the advantage that we can tweak it over time.