show checks in tray menu.

samples/ControlCatalog/App.xaml

@@ -34,10 +34,10 @@
           <NativeMenu>
             <NativeMenuItem Header="Settings">
               <NativeMenu>
-                <NativeMenuItem Header="Option 1" ToggleType="Radio" Command="{Binding ToggleCommand}" />
-                <NativeMenuItem Header="Option 2" ToggleType="Radio" Command="{Binding ToggleCommand}" />
+                <NativeMenuItem Header="Option 1" ToggleType="Radio" IsChecked="True" Command="{Binding ToggleCommand}" />
+                <NativeMenuItem Header="Option 2" ToggleType="Radio" IsChecked="True" Command="{Binding ToggleCommand}" />
                 <NativeMenuItemSeparator />
-                <NativeMenuItem Header="Option 3" ToggleType="CheckBox" Command="{Binding ToggleCommand}" />
+                <NativeMenuItem Header="Option 3" ToggleType="CheckBox" IsChecked="True" Command="{Binding ToggleCommand}" />
                 <NativeMenuItem Icon="/Assets/test_icon.ico" Header="Restore Defaults" Command="{Binding ToggleCommand}" />
               </NativeMenu>
             </NativeMenuItem>