Protocol v23

[stephaniehobson]

Associated GitHub task.

We're going to do some major renovations to Protocol to improve maintainability.

• Rename "title" to "heading"
• Rename "desc" to "body"
• Use CSS logical properties (start/end and block/inline)
  ** Rename classes and mixins to reflect logical names
• Standardize our focus support by using :focus-visible instead of :focus.
• Fix the Sass mixed-decls warnings and un-pin the Sass version

Once that's done before publishing we need to:

• Review the unsupported experience and give it some basic styles/support.
• Make sure the Firefox theme didn't get broken.

┆Issue is synchronized with this Jira Task
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