Add support for priority

Set default title to topic unique, as displayed in subscriptions list, if not provided
Increase toast timeout to 5 seconds

ntfysh_client/Notifications/NotificationReceiveEventArgs.cs

@@ -4,13 +4,17 @@ namespace ntfysh_client.Notifications
 {
     public class NotificationReceiveEventArgs : EventArgs
     {
+        public SubscribedTopic Sender { get; }
         public string Title { get; }
         public string Message { get; }
+        public NotificationPriority Priority { get; set; }
 
-        public NotificationReceiveEventArgs(string title, string message)
+        public NotificationReceiveEventArgs(SubscribedTopic sender, string title, string message, NotificationPriority priority)
         {
+            Sender = sender;
             Title = title;
             Message = message;
+            Priority = priority;
         }
     }
 }