Summary:
This is one of the last feature that is missing from native animated, it was already supported on Android and this implementation is based on it.
**Test plan**
Test that the existing decay animation example now works on iOS
Run unit tests
Closes https://github.com/facebook/react-native/pull/13368
Differential Revision: D4938061
Pulled By: javache
fbshipit-source-id: 36b57b1029a542e9daf21e048a06d3b3347e9659
Janic Duplessis