* Attaches a listener to remote notification events while the app is running
* in the foreground or the background.
*
* Valid events are:
*
* - `remoteNotificationsRegistered` : Fired when the user registers for remote notifications. The handler will be invoked with a hex string representing the deviceToken.
* - `notificationReceivedForeground` : Fired when a notification (local / remote) is received when app is on foreground state.
* - `notificationOpened`: Fired when a notification (local / remote) is opened.
* - `pushKitNotificationReceived` : Fired when a pushKit notification received when app is both on foreground and background state.