[BSv5] Reintroduce RTL support using 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.

• Drop import of custom Docsy RTL styling, which was designed for Bootstrap v4 - [BSv5] Drop import of rtl/main #1443
• Adjust build scripts to support RTL, possibly in a manner similar to Bootstrap, e.g.:
  https://github.com/twbs/bootstrap/blob/cf9454caa00872899215603e5e036d9a824b1b11/package.json#L46

Notes:

• Consider using /*rtl*/ directives to, e.g., adjust (prepend) to font paths, etc.
• Context: Upgrade to Bootstrap 5.2 #470
• Incorrect auto margins on RTL languages #829 will probably be obsolete once we have the updated support
• 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

Related:

• Logo Overlaps with Menu in RTL Languages kubernetes/website#45077

[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.

[mboukhalfa]

+1 this important since Arabic localization is in progress and expected to be alive on k8s website but the RTL issues are blocking even the preview of the progress ! this issue will greatly help