feat: setup demo.

demo/Ursa.Demo/ViewModels/DialogDemoViewModel.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Windows.Input;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Ursa.Controls;
+
+namespace Ursa.Demo.ViewModels;
+
+public class DialogDemoViewModel: ObservableObject
+{
+    public ICommand ShowLocalOverlayDialogCommand { get; }
+    public ICommand ShowGlobalOverlayDialogCommand { get; }
+
+    public DialogDemoViewModel()
+    {
+        ShowLocalOverlayDialogCommand = new RelayCommand(ShowLocalOverlayDialog);
+        ShowGlobalOverlayDialogCommand = new RelayCommand(ShowGlobalOverlayDialog);
+    }
+
+    private async void ShowGlobalOverlayDialog()
+    {
+        await DialogBox.ShowOverlayAsync<Banner, DateTime>(DateTime.Now, "GlobalHost");
+    }
+
+    private async void ShowLocalOverlayDialog()
+    {
+        await DialogBox.ShowOverlayAsync<Banner, DateTime>(DateTime.Now, "LocalHost");
+    }
+}