add groupbox style

HandyControlDemo/Data/MessageToken.cs

@@ -94,6 +94,8 @@
 
         public static readonly string SliderDemoCtl = nameof(SliderDemoCtl);
 
+        public static readonly string GroupBoxDemoCtl = nameof(GroupBoxDemoCtl);
+
         public static readonly string CommonWindow = nameof(CommonWindow);
 
         public static readonly string CustomNonClientAreaWindow = nameof(CustomNonClientAreaWindow);

HandyControlDemo/Data/MessageToken.tt

@@ -52,7 +52,8 @@ var styleList = new List<string>
 	"RadioButtonDemoCtl",
 	"NaiveScrollViewerDemoCtl",
 	"BrushDemoCtl",
-	"SliderDemoCtl"
+	"SliderDemoCtl",
+	"GroupBoxDemoCtl"
 };
 var windowList = new List<string>
 {