Summary:
Implements the Appearance native module as discussed in https://github.com/react-native-community/discussions-and-proposals/issues/126.
The purpose of the Appearance native module is to expose the user's appearance preferences. It provides a basic get() API that returns the user's preferred color scheme on iOS 13 devices, also known as Dark Mode. It also provides the ability to subscribe to events whenever an appearance preference changes.
The name, "Appearance", was chosen purposefully to allow for future expansion to cover other appearance preferences such as reduced motion, reduced transparency, or high contrast modes.
Changelog:
[iOS] [Added] - The Appearance native module can be used to prepare your app for Dark Mode on iOS 13.
Reviewed By: yungsters
Differential Revision: D16699954
fbshipit-source-id: 03b4cc5d2a1a69f31f3a6d9bece23f6867b774ea