feat: add generated binding documentation

[ianprime0509]

Closes #13

TODO:

• Autodoc doesn't handle module names containing . properly (probably solve this when implementing URL escaping) (WIP: https://github.com/ianprime0509/zig/tree/autodoc-url-escape)
• Autodoc displays aliased functions using the aliasee name (e.g. gtk_box_new), not the alias name (e.g. new)
• Handling docs through a compilation step with -femit-docs has unintended consequences, it tries to look up system libraries to link via pkg-config even though nothing needs to be linked
• Root module page is ugly
  • One solution is https://github.com/ianprime0509/zig/tree/multi-module-home, but since there must always be a root module anyway, maybe this isn't actually a good idea as-is