Automatically switch app language based on device language.

[auroursa]

Let’s introduce a package react-native-localization-settings to make the app’s language selectable in the device settings（Update: It’s not required, but I think it could improve user experience).

Based on expo-localization, the app language can automatically follow system language. For example, if the device language is set to Japanese, the app will automatically switch to Japanese (instead of English), similar to our web matches the browser language.

I’ve already tested this on Android, and it works well. It should work well on iOS, but I haven't had the opportunity to test it.