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.

• [x] Better homepage
• [x] Versioned documentation ahead of 4.5 and 5.0
  • [x] Enable versioning
  • [x] Versioned API links
  • [x] Build a version agnostic index page (index.md -> home.md?)
  • [x] Default page for missing versioned pages
  • [ ] Rendering of version on unversioned pages?
  • [x] http4s style redirects so that /latest -> /4.4, / -> /latest?
  • [x] 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)
• [x] More mdocing!
• [x] Guide to API expanded
  • [x] Parsley
  • [x] character
  • [x] combinator
  • [x] expr
  • [x] token
  • [x] errors
  • [x] registers
  • [x] genericbridges
  • [x] implicits
  • [x] position
  • [x] debug
• [x] 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
• [x] Landing page?
• [ ] Light-theme syntax highlighting?
• [ ] Styling for PDF and fixes?