add new demo view which can change the property

demo/Ursa.Demo/Pages/NumericUpDownDemo.axaml.cs

@@ -1,6 +1,9 @@
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
+using System;
+using System.Diagnostics;
+using Ursa.Controls;
 using Ursa.Demo.ViewModels;
 
 namespace Ursa.Demo.Pages;
@@ -11,5 +14,12 @@ public partial class NumericUpDownDemo : UserControl
     {
         InitializeComponent();
         DataContext = new NumericUpDownDemoViewModel();
+        numd.ValueChanged += Numd_ValueChanged;
+    }
+
+    private void Numd_ValueChanged(object? sender, ValueChangedEventArgs<uint> e)
+    {
+        Trace.WriteLine($"{(sender as NumericUIntUpDown).Name} {e.OldValue} {e.NewValue}");
+
     }
 }