Function onTokenReceived

onTokenReceived(input): EventListenerRemover
Registers a listener that will be triggered when a token is received. A token will be received:
1. On every app launch, including the first install
2. When a token changes (this may happen if the service invalidates the token for any reason)
Parameters
- input: OnTokenReceivedHandler
  A callback handler to be invoked with the token.
Returns EventListenerRemover
- An object with a remove function to remove the listener.
Example
```
// Register a listener
onTokenReceived(message => {
  doSomething(message);
});
```
Example
```
// Register multiple listeners
onTokenReceived(message => {
  doSomething(message);
});

onTokenReceived(message => {
  doSomethingElse(message);
});
```