Wiki Improvements

[j-mie6]

While the new Wiki has been published, it needs modernisation, including bringing it up to scratch with the 4.3 series.

• Better homepage
• Versioned documentation ahead of 4.5 and 5.0
  • Enable versioning
  • Versioned API links
  • Build a version agnostic index page (index.md -> home.md?)
  • Default page for missing versioned pages
  • Rendering of version on unversioned pages?
  • http4s style redirects so that /latest -> /4.4, / -> /latest?
  • Change header template so that we can change the tab name (https://typelevel.org/Laika/latest/03-preparing-content/03-theme-settings.html#customizing-template-fragments)
• More mdocing!
• Guide to API expanded
  • Parsley
  • character
  • combinator
  • expr
  • token
  • errors
  • registers
  • genericbridges
  • implicits
  • position
  • debug
• Tutorial patched up to remove parts now covered by API guide, and modernised with 4.0 series API
• Cheatsheet should get RST tables for better colouring and formatting support
• Landing page?
• Light-theme syntax highlighting?
• Styling for PDF and fixes?