Add support for "app languages" on Android

[abejfehr]

Why it is needed?

It's nice to be able to choose a language on a per-app basis instead of setting the whole OS, and it looks like that's possible now on Android: https://developer.android.com/guide/topics/resources/app-languages

Possible implementation

No response

Code sample

No response

[zoontek]

@abejfehr It's already supported. Android now allow the user to overrides the app language in app settings and it updates what's returned by existing react-native-localize functions.

EDIT: Hmmm, I forget Android API are often stupidly designed. Will investigate on extras setApplicationLocales() and getApplicationLocales(). But if this allow overriding from the app directly, this is a terrible feature for user experience.