Restart of and contribution to #1442. Recovers from changes to the following PRs:
2002 - updates layouts/partials/head-css.html
2018 - drops RTL "adjustment", which is no longer necessary
With this PR, each page is linked to a single style file, either the LTR version (main.css) or an RTL version (main.rtl.css), created from the LTR version piped through rtlcss
Ran Prettier over Multi-linguage UG page, and cleaned up the front matter. No content changes yet.
2002 - updates
layouts/partials/head-css.html2018 - drops RTL "adjustment", which is no longer necessary
main.css) or an RTL version (main.rtl.css), created from the LTR version piped through rtlcss