updated adding custom items sample details

Author: mageshyadavm

README.md

@@ -7,3 +7,4 @@ This repository contains samples that demonstrate built-in functionalities of Dr
 * **<a href="Samples/Add-Menu-Items">Adding Menu Items</a>** - This demo explains how to bind menu items to dropdown button control.
 * **<a href="Samples/Data-Binding">Data Binding</a>** - This demo explains how to bind data to dropdown menu group using XAML data binding and consume menu item command actions.
 * **<a href="Samples/Command-Binding">Command Binding</a>** - This demo explains how to provide command binding for dropdown menu items to perform any action while clicking the same.
+* **<a href="Samples/Add-Custom-Items">Adding Custom Menu Items</a>** - This demo explains how to add custom dropdown menu items and handle visibility of custom items IconBar in dropdown control.