feat: add demo.

demo/Ursa.Demo/ViewModels/PopConfirmDemoViewModel.cs

@@ -0,0 +1,31 @@
+using System.Windows.Input;
+using Avalonia.Controls.Notifications;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Ursa.Controls;
+
+namespace Ursa.Demo.ViewModels;
+
+public partial class PopConfirmDemoViewModel: ObservableObject
+{
+    internal WindowToastManager? ToastManager { get; set; }
+    
+    public ICommand ConfirmCommand { get; }
+    public ICommand CancelCommand { get; }
+    
+    public PopConfirmDemoViewModel()
+    {
+        ConfirmCommand = new RelayCommand(OnConfirm);
+        CancelCommand = new RelayCommand(OnCancel);
+    }
+    
+    private void OnConfirm()
+    {
+        ToastManager?.Show(new Toast("Confirmed"), type: NotificationType.Success, classes: ["Light"]);
+    }
+    
+    private void OnCancel()
+    {
+        ToastManager?.Show(new Toast("Canceled"), type:NotificationType.Error, classes: ["Light"]);
+    }
+}