feat: add auto tick sample.

demo/Ursa.Demo/ViewModels/ClockDemoViewModel.cs

@@ -1,6 +1,31 @@
-namespace Ursa.Demo.ViewModels;
+using System;
+using System.Timers;
+using CommunityToolkit.Mvvm.ComponentModel;
 
-public class ClockDemoViewModel
+namespace Ursa.Demo.ViewModels;
+
+public partial class ClockDemoViewModel: ObservableObject, IDisposable
 {
+    private Timer _timer;
     
+    [ObservableProperty] private DateTime _time;
+    public ClockDemoViewModel()
+    {
+        Time = DateTime.Now;
+        _timer = new Timer(1000);
+        _timer.Elapsed += TimerOnElapsed;
+        _timer.Start();
+    }
+
+    private void TimerOnElapsed(object? sender, ElapsedEventArgs e)
+    {
+        Time = DateTime.Now;
+    }
+
+    public void Dispose()
+    {
+        _timer.Stop();
+        _timer.Elapsed -= TimerOnElapsed;
+        _timer.Dispose();
+    }
 }