Summary:
Current version wasn't triggering any sound when a local notification was fired. I added the possibility to provide a custom sound and fallback to the default iOS sound if not provided.
Closes https://github.com/facebook/react-native/pull/4836
Reviewed By: svcscm
Differential Revision: D2807381
Pulled By: bestander
fb-gh-sync-id: c25e8f3c30a0714a5d9558c0c1fe344d0e93321e