follow up to css revision

[pkra]

Follow up to https://github.com/w3c/aria/pull/2410.

Reviewing the spec css identified various other issues. Let's collect them here

• [ ] [spec HTML] nested .rfc2119 -- look like simple authoring errors
  • ARIA: https://github.com/w3c/aria/blob/077621f4676b386a1a1fba804e8f20b964f67cbc/index.html#L423
  • other specs have similar<em class="rfc2119">....</em> which should be removed.
• [ ] [spec HTML] highlight.js failing to identify snippet language -- add explicit source info
  • e.g. several .abnf matches for what's actually HTML
  • how to: https://github.com/speced/respec/wiki/ReSpec-Editor's-Guide#examples
• [ ] aria.js: dl with .compact (for lists of roles and states&props - 5.4, 6.8) - class no longer used
• [ ] [respec?] configure highlightjs theme (to be more accessible)