now hc styles can be referenced in window.resource

by the way, supported multiple themes at the same time, It may be related to #574

src/Shared/HandyControlDemo_Shared/Resources/DemoTheme.cs

@@ -11,9 +11,9 @@ namespace HandyControlDemo.Resources
         public override ResourceDictionary GetSkin(SkinType skinType) =>
             ResourceHelper.GetSkin(typeof(App).Assembly, "Resources/Themes", skinType);
 
-        public override ResourceDictionary GetTheme() => new ResourceDictionary
+        public override ResourceDictionary GetTheme() => new Lazy<ResourceDictionary>(() => new ResourceDictionary
         {
             Source = new Uri("pack://application:,,,/HandyControlDemo;component/Resources/Themes/Theme.xaml")
-        };
+        }).Value;
     }
 }