Added virtual accessor to HamburgerMenuButton.UpdateCheckedState method

src/Cimbalino.Toolkit.Controls (UWP)/Controls/HamburgerMenuButton.cs

@@ -116,7 +116,7 @@ protected override void OnToggle()
         /// </summary>
         /// <param name="sourcePageType">The data type of the source page.</param>
         /// <param name="parameter">Any Parameter object passed to the target page for the navigation.</param>
-        public void UpdateCheckedState(Type sourcePageType, object parameter)
+        public virtual void UpdateCheckedState(Type sourcePageType, object parameter)
         {
             this.IsChecked = NavigationSourcePageType == sourcePageType && NavigationParameter == parameter;
         }