updated the style of menu

src/Shared/HandyControl_Shared/Themes/Styles/Style.xaml

@@ -18,6 +18,7 @@
         <ResourceDictionary Source="TabControl.xaml"/>
         <ResourceDictionary Source="ListBox.xaml"/>
         <ResourceDictionary Source="Loading.xaml"/>
+        <ResourceDictionary Source="Menu.xaml"/>
         <ResourceDictionary Source="ContextMenu.xaml"/>
         <ResourceDictionary Source="ToolTip.xaml"/>
         <ResourceDictionary Source="Expander.xaml"/>