Docs overhaul 2

[cspotcode]

Splitting out from #1682

• Bring in #1674
  • where appropriate, update website categorization to match --help
• consider unifying --help descriptions, website descriptions, and jsdoc descriptions
  • find a way to merge all descriptions into one document for inspection
  • easily see where they differ and where to unify
• finish the npx and yarn dlx pages
  • read my TODO notes in the markdown
  • re-add to sidebar.js
  • uncomment link in troubleshooting.md
• consider avoiding broken links. How?