How to export Godot 4 documenting comments to XML?

**Your Godot version:**
4.0.alpha14

**Issue description:**
The docs page for "[documenting comments](https://docs.godotengine.org/en/latest/tutorials/scripting/gdscript/gdscript_documentation_comments.html)" says we can export our own GDScript generated documentation as XML in the end of the first paragraph, but it never explains how to do it.

Am I missing something I should already know?
Or is that feature not ready yet?

If this is already possible it would be neat to add a section in that page for how to export it to XML.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/latest/tutorials/scripting/gdscript/gdscript_documentation_comments.html