version switcher on deployed website disappeared

[rgommers]

Almost certainly caused by gh-735.

Also xref a related issue with a JS warning about the search results, which was also due to a Sphinx version upgrade: data-apis/data-apis.github.io#24.

[rgommers]

This works in the demo site of the theme (see [here](https://bashtage.github.io/sphinx-material/customization.html, also for docs on version dropdown usage).

We have a slightly unusual setup here, but it's not clear what changed beyond an upgrade of Sphinx. Things do seem to land in the right places in the gh-pages branch.

A bit of info:

• the dropdown was added in Add a version menu to the Sphinx build #394,
• Sphinx config is at

  array-api/src/_array_api_conf.py

  Lines 174 to 175 in fa04c35

  	"version_dropdown": True,
  	"version_json": "../versions.json",

• versions are specified in https://github.com/data-apis/array-api/blob/main/spec/_ghpages/versions.json
• running make in the root of the repo reproduces the problem locally
• debugging the deployed site in the browser shows Uncaught ReferenceError: $ is not defined, which points at the add_version_dropdown line of:

  <script src="_static/javascripts/version_dropdown.js"></script>
  <script>
    var json_loc = "../versions.json",
        target_loc = "../",
        text = "Versions";
    $( document ).ready( add_version_dropdown(json_loc, target_loc, text));
  </script>

Someone with more JavaScript skills can take it from here I hope:)

[asmeurer]

I think it has to do with jquery. There was some change in sphinx at some point where they stopped shipping it or something like that.

[asmeurer]

See sympy/sympy#24989. The fix here is probably the same.