[chore:] changes from github

MainWindow.axaml.cs

@@ -56,10 +56,9 @@ public partial class MainWindow : Window
         //await MessageBox.Show(_instance, $"{result.Count} Einträge fehlerhaft.", "Fertig");
     }
 
-
     private void MnuExit_OnClick(object? sender, RoutedEventArgs e)
     {
-        throw new NotImplementedException();
+        Environment.Exit(0);
     }
 
     private void MnuAbout_OnClick(object? sender, RoutedEventArgs e)