Version warning banner shows on stable docs

[psobolewskiPhD]

🐛 Bug

With #531 merged the warning banner now shows on napari.org with stable version:

Clicking the switch to stable doesn't do anything, but reloads the page.

The warning banner also correctly shows when the latest version is selected, but not when an old version is selected.

[psobolewskiPhD]

Note after dismissing it once it never shows up again, even with reload, etc. so maybe that's why we missed this.

[jni]

Hmm. Should we revert this in the meantime?

[jax-sobolewski]

The version switcher looks ok
https://napari.org/dev/_static/version_switcher.json
vs the docs:
https://pydata-sphinx-theme.readthedocs.io/en/stable/user_guide/announcements.html#version-warning-banners
only difference is the order of where preferred is placed?
What's odd is the name replacement does work, which I think also uses the preferred flag.

[jax-sobolewski]

Here's numpy by comparison:
https://numpy.org/doc/_static/versions.json
again everything the same but the order. and theirs works:
no banner: https://numpy.org/doc/stable/index.html
banner: https://numpy.org/devdocs/index.html

[psobolewskiPhD]

Lol wrong account!

[psobolewskiPhD]

OK, shower thought: it's because of the copying of dev pages.
Looks to be true! The banner doesn't show on /stable pages that weren't copied over.
And it's in the HTML to show the banner on the homepage:
DOCUMENTATION_OPTIONS.show_version_warning_banner = true;
I think there is already a script doing some tweaking of the copied pages, so need to check this too.

[psobolewskiPhD]

Boom: we need a line like this:
https://github.com/napari/napari.github.io/blob/4e4b6c60d2465bccda2f979123147b0f64120457/.github/workflows/unversioned_pages.yml#L41

Except that for whatever reason the show_version_warning_banner on napari.org lines have a line break so sed seems not ideal.

        DOCUMENTATION_OPTIONS.show_version_warning_banner =
            true;

[psobolewskiPhD]

The same line is also broken over 2 lines the same way in the numpy docs, so it's something the theme is doing -- even though that's not the longest <script> section line.