[Docs] Add version dropdown to the pkgdown (R) docs

[asfimport]

The Python and C++ documentation have support for serving multiple versions of the docs and switching between them thanks to the newly added version switcher. The same doesn't apply to the R docs as they are not implemented in Sphinx and thus can't benefit from the version switcher implemented for Sphinx.

We should provide an equivalent version switcher for the R docs.

We are already hosting multiple versions of the R docs:

• Stable: https://arrow.apache.org/docs/r/

• Dev: https://arrow.apache.org/docs/dev/r/

• Old releases: https://arrow.apache.org/docs/5.0/r/ etc.

  So the need is simply for a UI element to enable users to easily navigate between these.

  Relevant pkgdown issue: Consider readthedocs style handling of multiple versions r-lib/pkgdown#1373

  Possible implementation ideas:

• https://insightsengineering.github.io/r.pkg.template/ does it with a dropdown in the main header, I suppose that's something we could do as well (although that would be some manual work to update it in _pkgdown.yml before each version)

• from @ianmcook: I don’t have an example of extra.js being used specifically for version switching, but we already have an extra.js we’re using for a different purpose: https://github.com/apache/arrow/blob/master/r/pkgdown/extra.js. I believe it would be relatively straightforward to use jQuery to replace the static version <span> which looks like this

  <span class="version label label-default" data-toggle="tooltip" data-placement="bottom" title="" data-original-title="Released version">6.0.1</span>

  with a <select> that would allow users to navigate to other versions of the R docs

  If it is necessary to hard-code R package versions in a file to achieve this, then we could automate the updating of these hard-coded versions at each release through dev/release/utils-prepare.sh, and add a test confirming the update at dev/release/01-prepare-test.rb.

Reporter: Nicola Crane / @thisisnic
Assignee: Nicola Crane / @thisisnic

Related issues:

• [Doc] Add support for serving multiple versions of the R documentation (is duplicated by)
• [Docs] Automate incrementing of package version for R and non-R version switchers (relates to)

PRs and other links:

• GitHub Pull Request #12172

_{Note: This issue was originally created as ARROW-14338. Please see the migration documentation for further details.}

[asfimport]

Ian Cook / @ianmcook:
After (but only after!) this is implemented, we should make the link to the R docs from the main project docs preserve the version.

So for example the R link...
... from https://arrow.apache.org/docs/ would go to https://arrow.apache.org/docs/r/
... from https://arrow.apache.org/docs/dev/ would go to https://arrow.apache.org/docs/dev/r/
... from https://arrow.apache.org/docs/5.0/ would go to https://arrow.apache.org/docs/5.0/r/
and so on.

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 12172
#12172

[asfimport]

Ian Cook / @ianmcook:
This is working great in Chrome but I can't get it to work in Safari on macOS. Could someone else please try it in Safari to confirm whether there's a problem?

[asfimport]

Nicola Crane / @thisisnic:
Not just you @ianmcook, thanks for reporting this. Have opened ARROW-15819