added utfsequence to react-native exports (#20955)

Summary:
Fixes #20935

Added UTFSequence module to React-Native exports. Put it under // APIs but I'm not certain if it belongs there.
Pull Request resolved: #20955

Differential Revision: D13396903

Pulled By: cpojer

fbshipit-source-id: 29cb2ee1431132bd7ca4973fecb0025cd6303a14

Author: byronluk

Libraries/react-native/react-native-implementation.js

@@ -282,6 +282,9 @@ module.exports = {
   get unstable_batchedUpdates() {
     return require('ReactNative').unstable_batchedUpdates;
   },
+  get UTFSequence() {
+    return require('UTFSequence');
+  },
   get Vibration() {
     return require('Vibration');
   },