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/ViewModels/MainWindowViewModel.cs

@@ -65,6 +65,8 @@ public class MainWindowViewModel : MyReactiveObject
 
     [Reactive] public bool BlIsWindows { get; set; }
 
+    [Reactive] public bool BlNewUpdate { get; set; }
+
     #endregion Menu
 
     #region Init
@@ -251,6 +253,11 @@ public class MainWindowViewModel : MyReactiveObject
             .ObserveOn(RxSchedulers.MainThreadScheduler)
             .Subscribe(async blProxy => await UpdateSubscriptionProcess("", blProxy));
 
+        AppEvents.HasUpdateNotified
+            .AsObservable()
+            .ObserveOn(RxSchedulers.MainThreadScheduler)
+            .Subscribe(async bl => BlNewUpdate = bl);
+
         #endregion AppEvents
 
         _ = Init();