Localization

From what I can see, there is no documentation on the expected localization workflow. I can put something together here if it sounds appropriate for the book.

On my side, I haven't figured out how to extract the localization strings from the Rust files yet. These aren't standard gettext functions, but I know it is configurable for gettext so there is probably a way to extract and merge it with the pot file from Godot. I just need to find the specifics.