feat: implement command, fix icon foreground in light mode.

demo/Ursa.Demo/ViewModels/BreadcrumbDemoViewModel.cs

@@ -1,5 +1,8 @@
 using System.Collections.ObjectModel;
+using System.Windows.Input;
 using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Ursa.Controls;
 
 namespace Ursa.Demo.ViewModels;
 
@@ -24,4 +27,14 @@ public class BreadcrumbDemoItem: ObservableObject
 {
     public string Section { get; set; }
     public string Icon { get; set; }
+    
+    public ICommand Command { get; set; }
+
+    public BreadcrumbDemoItem()
+    {
+        Command = new RelayCommand(() =>
+        {
+            MessageBox.ShowOverlayAsync(Section);
+        });
+    }
 }