Protocol v23

[stephaniehobson]

After Protocol 22 we're going to do some major renovations to improve maintainability. Here are a few issues that will likely be part of that:

Modernizing:

• Go all-in on CSS custom properties for themes, remove Sass variables #982
• Sass warnings generated by font mixins #998
• Refactor typography system to use CSS custom properties #1107
• Audit use of vendor prefix mixins #957
• use starts/ends and block/inline
• use focus-visible

Renaming:

• Rename "title" to "heading" #668
• Rename desc to body
• Rename v/h to block/inline
• Update component classes to use new naming standards #448
• Confusing naming for theme spacing variables #701

Theme updates:

• Do we still need Inter as fallback?