Localization Documentation

[jetpacktuxedo]

I was working on adding Brazilian Portuguese localizations for a labeler, but I'm not sure what language code to use for that. My instinct would be br, but IETF language tags don't split Brazil from Portugal and just uses pt for both. Bluesky uses Portuguese (BR) on the app side:

I wasn't able to find docs anywhere that lists what codes are accepted (or better a mapping of codes to countries), so I'm just kind of guessing right now.

Related, it may be nice to document what language setting needs to be flipped in the app in order to verify that the locales are working. I assume it should be the "Primary Language" setting?