Should be able to customize default channel name instead of hard-coded to "Firebase"

[jacobg]

https://github.com/chemerisuk/cordova-plugin-firebase-messaging/blob/0ecfae7c32eaca55f6368413f2275596191025b9/src/android/FirebaseMessagingPluginService.java#L61-L62C49

                notificationManager.createNotificationChannel(
                        new NotificationChannel(defaultNotificationChannel, "Firebase", NotificationManager.IMPORTANCE_HIGH));