Summary:
Ground work for allowing `font-variant`s. Currently allows switching between `tabular-nums` and `proportional-nums`. I will need guidance on how to test this, and a few pointers on code style (new to Objective C, and had to make one or two hacks).
Closes https://github.com/facebook/react-native/pull/9045
Reviewed By: majak
Differential Revision: D3664338
Pulled By: javache
fbshipit-source-id: 032f326c37ee6150348da2b33b6a3fc1988e8920
f951da912d