feat: initialize.

demo/Ursa.Demo/ViewModels/MainViewViewModel.cs

@@ -36,6 +36,7 @@ public class MainViewViewModel : ViewModelBase
             MenuKeys.MenuKeyKeyGestureInput => new KeyGestureInputDemoViewModel(),
             MenuKeys.MenuKeyLoading => new LoadingDemoViewModel(),
             MenuKeys.MenuKeyNavigation => new NavigationMenuDemoViewModel(),
+            MenuKeys.MenuKeyNumericUpDown => new NumericUpDownDemoViewModel(),
             MenuKeys.MenuKeyPagination => new PaginationDemoViewModel(),
             MenuKeys.MenuKeyTagInput => new TagInputDemoViewModel(),
             MenuKeys.MenuKeyTimeline => new TimelineDemoViewModel(),

demo/Ursa.Demo/ViewModels/MenuViewModel.cs

@@ -23,6 +23,7 @@ public class MenuViewModel: ViewModelBase
             new() { MenuHeader = "KeyGestureInput", Key = MenuKeys.MenuKeyKeyGestureInput },
             new() { MenuHeader = "Loading", Key = MenuKeys.MenuKeyLoading },
             new() { MenuHeader = "Navigation", Key = MenuKeys.MenuKeyNavigation },
+            new() { MenuHeader = "NumericUpDown", Key = MenuKeys.MenuKeyNumericUpDown },
             new() { MenuHeader = "Pagination", Key = MenuKeys.MenuKeyPagination },
             new() { MenuHeader = "TagInput", Key = MenuKeys.MenuKeyTagInput },
             new() { MenuHeader = "Timeline", Key = MenuKeys.MenuKeyTimeline },

demo/Ursa.Demo/ViewModels/NumericUpDownDemoViewModel.cs

@@ -0,0 +1,8 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace Ursa.Demo.ViewModels;
+
+public class NumericUpDownDemoViewModel: ObservableObject
+{
+    
+}