Your Godot version: 4.0.3

Issue description: No documentation about create GDExtension bindings

URL to the documentation page (if already existing):

While there is a documentation page about what GDExtension is and its difference with C++ modules and another page showing an example with the C++ GDExtension bindings, there is no page about creating bindings for a programming language and where to find and how to use the C GDExtension API. It would be very nice if one such page is added.

It doesn't have to be something very advanced and extreme but at least something basic to show developers how to create bindings for other languages.

Personally, this will be very important for me as I'm creating my own language and while it's still very very early and I haven't even publish it yet, I want the docs to be ready when I do so I can immediately start supporting Godot! Of course, languages that are out now are important as well!