add style and demo

src/Shared/HandyControlDemo_Shared/App.xaml.cs

@@ -53,6 +53,16 @@ namespace HandyControlDemo
                 Source = new Uri("pack://application:,,,/HandyControlDemo;component/Resources/Themes/Theme.xaml")
             });
             Current.MainWindow?.OnApplyTemplate();
+
+            Resources.MergedDictionaries.Clear();
+            Resources.MergedDictionaries.Add(new ResourceDictionary
+            {
+                Source = new Uri($"pack://application:,,,/HandyControl;component/Themes/Skin{skin.ToString()}.xaml")
+            });
+            Resources.MergedDictionaries.Add(new ResourceDictionary
+            {
+                Source = new Uri("pack://application:,,,/HandyControl;component/Themes/Theme.xaml")
+            });
         }
     }
 }