Push Token not received on each app launch following Amplify documentation

**Describe the content issue**:
Missing content - this page should include additional AppDelegate code to ensure that a push token is received on every app launch as intended.
```
- (void)applicationDidFinishLaunching:(UIApplication *)app {

// ....

// Register for remote notifications.
[[UIApplication sharedApplication] registerForRemoteNotifications];
}
```

or at least a note to point to this page:
https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/HandlingRemoteNotifications.html

**URL page where content issue is**:
https://docs.amplify.aws/gen1/react-native/build-a-backend/push-notifications/set-up-push-notifications/#update-your-application-delegate