Redo the 5zig docs.

[Andre601]

This is a rather big Pull request as it essentially rewrites the docs in some way or another.

Changelog

• Changed the whole publishing feature
  • The mkdocs-material symlink and the pymdownx folder have been removed in favour of a GitHub Action-based system.
  • Added .github/workflows/publish.yml which setups python, downloads mkdocs-material and its dependencies (including mkdocs and pymdown), and mkdocs-redirects, builds the pages and then pushes it to gh-pages
• Renamed folders and pages
  • Client_API -> client-api
  • Mod -> mod
  • Server_API -> server-api
  • Redirects have been established for the old folders and pages using the redirect plugin.
• Improved mkdocs.yml
  • Added missing nav section for navigation
  • Added additional feature flags which can be useful
  • Updated structure for material options
  • Added slate scheme for the theming (dark theme!).
  • Changed primary colour to amber. It shouldn't be an eyesore with dark theme now. :)
• Improved formatting of the different pages.