Add 'New Update' notification flow

Introduce a small update-notification feature: add AppEvents.HasUpdateNotified event and have TaskManager publish it when update messages exist. Add localized resource key (menuNewUpdate) and expose it in the ResUI designer; update resource files for several languages. In the UI, add a New Update button in MainWindow.xaml, wire its click to the existing check-update handler, bind its visibility to a new BlNewUpdate property on MainWindowViewModel, and subscribe the viewmodel to the new event. Also reset the notification flag after showing the Check Update dialog.

v2rayN/ServiceLib/Resx/ResUI.Designer.cs

@@ -1320,6 +1320,15 @@ namespace ServiceLib.Resx {
             }
         }
         
+        /// <summary>
+        ///   查找类似 New Update 的本地化字符串。
+        /// </summary>
+        public static string menuNewUpdate {
+            get {
+                return ResourceManager.GetString("menuNewUpdate", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   查找类似 Open the storage location 的本地化字符串。
         /// </summary>