Add markdown rendering for code blocks

Overview

Unbundled from !836 (comment 1740507529).

• Resolves a TODO for markdown rendering of code blocks,
• Combines with work from 63fc90d6 for the best of both when rendering code spans.
• Adds example markdown rendering in the design system since it can be tricky to see all the markdown styling in one place.

How to Test

• Review the example markdown in the design system Molecules -> Markdown section.
• Review markdown in several app contexts, for example:
  • About Page -> Top section.
  • Volume mount instructions after attaching a volume.
  • (A built Support request if supportInfoMarkdown is enabled.)

Screenshots