Documentation for bindings

[theCapypara]

It would be great if Biblioteca would provide binding specific documentation for at least Vala, GJS, PyGObject and gtk-rs.
In the simplest form it could do that by having links from all pages to the respective counterpart in these docs.

Biblioteca could also bundle offline versions of these if licensing allows.

Example for where Gtk-4.0's "GtkSwitch.set_active" would link to:

• Vala: https://valadoc.org/gtk4/Gtk.Switch.set_active.html
• GJS: https://gjs-docs.gnome.org/gtk40~4.0/gtk.switch#method-set_active
• PyGObject: https://lazka.github.io/pgi-docs/Gtk-4.0/classes/Switch.html#Gtk.Switch.set_active
• gtk-rs: https://gtk-rs.org/gtk4-rs/git/docs/gtk4/struct.Switch.html#method.set_active (this is probably the most complicated to link to, due to the different crates involved and structural differences / extension traits)

Related issues:

• Support web content #27 - would be required for properly displaying the content, especially if loaded from online sources
• API for browing to documentation #47 - such an API/URI schema could also support direcly loading the binding specific pages

[sonnyp]

Even more related #28
devdocs would be a good start - we'd get plenty of docs for free + GJS

Otherwise I think we can show those in webviews (we already have the bookmarks), maybe even crawl them and make an offline version easily.
But I wouldn't be in favor of building search, indexing, ... for each individual format.

I think our time would be better spent on either

1. Make devdocs or dashdoc for these
2. Share tooling between docs