Yellow box warning - requires main queue setup since it overrides `init` but doesn't implement `requiresMainQueueSetup`

### Steps to reproduce
Launch app with react-native-oauth in iOS (simulator can reproduce)

### Expected behavior
No Yellow Box Warning

### Actual behavior
Yellow Box Warning

### Environment
iOS
"react": "16.8.3",
"react-native": "0.59.10",
"react-native-oauth": "2.1.18",