Play an animation when the content of the badge is changed, and add the related demo.

HandyControlDemo/ViewModel/Controls/BadgeDemoCtlViewModel.cs

@@ -0,0 +1,25 @@
+using System.Windows.Input;
+using GalaSoft.MvvmLight;
+using GalaSoft.MvvmLight.CommandWpf;
+
+namespace HandyControlDemo.ViewModel.Controls
+{
+    public class BadgeDemoCtlViewModel : ViewModelBase
+    {
+        private int _count;
+
+        public int Count
+        {
+            get => _count;
+            set => Set(ref _count, value);
+        }
+
+        public ICommand CountCommand { get; }
+
+        public BadgeDemoCtlViewModel()
+        {
+            Count = 1;
+            CountCommand = new RelayCommand(() => Count++);
+        }
+    }
+}