feat: rewrite with Starlight

[zlataovce]

This is a rewrite using the Starlight documentation generator instead of Docusaurus.
The goal is to standardize the framework choice and look with our website (pending rewrite in Astro), improve performance, editing experience and maintainability (dropping Docusaurus hack-patches).

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TODO:

• TODOs in code
• Components
  • Javadoc - replaced with custom Markdown links (using a remark plugin)
  • SoftwareVersion - replaced with MDX import+constant replacement
  • Property - replaced with MDX import+constant replacement or removed altogether
  • VersionFormattedCode - replaced with a remark plugin (constants defined in astro.config.ts)
  • Configuration-related components
• Pages
  • /paper/admin
    • Configuration reference
    • Vanilla-like experience
    • Permissions reference
  • /paper/dev
    • API pages
  • /paper/contributing
  • /folia/admin
  • /velocity/admin
  • /velocity/dev
    • Component API (passthrough to the Paper pages)
  • /waterfall
    • Configuration
  • /misc
    • Start script generator
    • Item command converter
  • Create index.md(x) for each subdirectory - Docusaurus generates index pages, Starlight does not
• Drop Starlight patch in favor of Add support for custom icons withastro/starlight#3024
• Remove versioned pages, introduce version tag
• Rewrite all links to absolute ones and enable link validator
• Revise theme colors
• Add mermaid diagram support (replaced with D2)
• Rename .mdx -> .md where no MDX features are used (for better future portability)

[github-actions]

built with Refined Cloudflare Pages Action

⚡ Cloudflare Pages Deployment

Name	Status	Preview	Last Commit
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[kashike]

I have no issues with us migrating to Starlight - this looks good so far.

[zlataovce]

this is now mergeable (ready for review), as Starlight has merged and released the last needed feature

(project icons are currently patched in and should be replaced with withastro/starlight#3024, but the patch can be dropped whenever, not a blocker)

[EterNityCH]

This is epic 🔥

[kashike]

@zlataovce Before merging, please fix the orange. 🍊

[olijeffers0n]

Currently looks like this on mobile

[Strokkur424]

The rotating item display entitiy under /paper/dev/display-entities/#interpolation is also a bit too big I feel like. You could either crop it a bit so that it doesn't take up as much height, or reduce its size.