Reintroduce RTL support using BSv5 RTLCSS

[chalin]

In our move to Bootstrap v5 (BSv5), we are adopting the Bootstrap approach to RTL, as described in https://getbootstrap.com/docs/5.3/getting-started/rtl/. The good news is that we don't have to rename all properties that have logical counterparts (at least for now), since RTLCSS handles their translation appropriately.

24H2 work

• Starting over with the strategy of using a single "main" CSS file per page, using an adapted RTL CSS for RTL pages:
  RTL support via a single main style file #2093
• Review of 24H1 PRs that might need to be totally or partially reverted:
  • [BSv5] Drop import of rtl/main #1443 - nothing to revert
  • Add RTL support using BSv5 #2002 - ok except for layouts/partials/head-css.html, which is being reworked.
    Reverted via RTL support via a single main style file #2093
  • [RTL] Drop unused style files #2020 & [RTL] Add CHANGELOG entry and drop RTL for en #2021 - nothing to revert
  • [RTL] Fix top-nav position #2018 - reverted via RTL support via a single main style file #2093
  • Ensure RTL works when Docsy is used via Hugo modules #2025 - reverted via [RTL] Drop unused BS asset and scripts to fetch it #2096
• Create an rtl branch to be used during development
  Branch preview: https://rtl--docsydocs.netlify.app/
• On rtl branch, set the en language as rtl for testing purposes - [RTL] UG: set en to rtl for testing purposes #2095
• Old 24H1 issues that go away with RTL support via a single main style file #2093:
  • [RTL] Light/dark-mode dropdown menu position is pinned to the right on narrow displays #2003
  • [RTL] Footer icon-group placement and spacing issues #2005
• Test it out on the Docsy example
• Cleanup - [RTL] Drop unused BS asset and scripts to fetch it #2097
• Update the UG - [UG] Add RTL config section #2098

24H1 work - some of it reverted in H2

Entries processed (either ok as is, or reverted in whole or part), are marked with ⤴.

• ⤴ Drop import of custom Docsy RTL styling, which was designed for Bootstrap v4 - [BSv5] Drop import of rtl/main #1443
• ⤴ Add RTL support using BSv5 #2002, fixing
  [RTL] Breadcrumb separator is in the wrong place #2004
• ⤴ [RTL] Drop unused style files #2020
  [RTL] Add CHANGELOG entry and drop RTL for en #2021
• ⤴ [RTL] Fix top-nav position #2018
  • Incorrect auto margins on RTL languages #829
  • The menu does not switch sides when the site changes to RTL #2011
• ⤴ Ensure RTL works when Docsy is used via Hugo modules #2025

---

Related:

• Logo Overlaps with Menu in RTL Languages kubernetes/website#45077
• Right-to-left language support kubernetes/website#22730

Notes:

• Context: Upgrade to Bootstrap 5.2 #470
• Would a switch to Bootstrap's RTL solution help address the following as well:
  docsy theme still causes outgoing connections to Google Fonts for Arabic and Hebrew languages matrix-org/docsy#1?
  Related(?): Support non-CDN resources #605

Other:

• https://github.com/twbs/bootstrap/blob/cf9454caa00872899215603e5e036d9a824b1b11/package.json#L46

[nate-double-u]

I think we may need some upstream help to support an Arabic localization for the kubernetes.io website (using Docsy as a theme).

• Create basic structure and translate home for Arabic kubernetes/website#44902

And to link this issue to the Kubernetes site more generally, I think solving this issue will also go toward solving kubernetes/website#22730

/cc @mboukhalfa, @a-mccarthy, @sftim

[chalin]

All: as I mentioned in Slack, BS's RTL support is experimental:

Bootstrap's RTL feature is still experimental and will evolve based on user feedback. Spotted something or have an improvement to suggest? Open an issue, we'd love to get your insights.

[a-mccarthy]

+1 @nate-double-u, this would help enable new languages that have started or expressed interest in localizating Kubernetes documentation.

cc: @seokho-son

[chalin]

@a-mccarthy @seokho-son : if you (and members of your community) could upvote this issue, it would help me assess the relative importance of the feature. Thanks.