Include the GUI library

Update the zip index.html to include the Babylon.js GUI library.

Playground/zipContent/index.html

@@ -6,9 +6,11 @@
         <title>Babylon.js sample code</title>
         <!-- Babylon.js -->
         <script src="https://www.babylonjs.com/hand.minified-1.2.js"></script>
+        <script src="https://preview.babylonjs.com/gui/babylon.gui.min.js"></script>
         <script src="https://preview.babylonjs.com/cannon.js"></script>
         <script src="https://preview.babylonjs.com/oimo.js"></script>
         <script src="https://preview.babylonjs.com/babylon.js"></script>
+        
         <style>
             html, body {
                 overflow: hidden;