Interface that should be implemented to receive notification change callbacks from the NotificationProvider

A trivial implementation of NotificationListener would be:

// A caplin.streamlink.alerts.NotificationListener that can handle
// every possible callback.
//
// This trivial implementation just logs the callbacks
//

var notificationService = new caplin.streamlink.alerts.NotificationService(streamlink);

notificationService.addListener(
{
        onNotification: function(notification)
        {
                console.log("onNotification()(" + notification.toString() + ")");
        },
        
        onNotificationRemoved: function(notification)
        {
                console.log("onNotificationRemoved(" + notification.toString() + ")");
        },
        
        onServiceStatus: function(status)
        {
                console.log("onServiceStatus(" + status + ")");
        }
});