feat: add generated binding documentation

[ianprime0509]

Closes #13

TODO:

• Autodoc displays aliased functions using the aliasee name (e.g. gtk_box_new), not the alias name (e.g. new)
  • Unless/until Proposal: Add linkname in addition to linksection ziglang/zig#19999 is accepted and implemented, probably the best way to handle this is just to make a passthrough wrapper function. It's not as pretty, but as long as the wrapper is callconv(.C), I can't think of any use-case that would actually be affected by this. This doesn't work, because I forgot C varargs exist and work the way they do; they can't simply be passed through with a wrapper.
  • There is a quick and dirty "fix" for this on my new "experimental" Autodoc fork: https://github.com/ianprime0509/autodoc-experimental
• 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
• Autodoc considers opaque types to be namespaces(?)