Merge pull request #6245 from microsoft/cre8ivepark-patch-1

Update Examples Hub README to provide information on Extension package

Author: David Kline

Documentation/README_ExampleHub.md

@@ -6,6 +6,9 @@ MRTK Examples Hub is a Unity scene that makes it easy to experience multiple sce
 
 **MRTKExamplesHub.unity** is the container scene that has shared components including ``MixedRealityToolkit`` and ``MixedRealityPlayspace``. **MRTKExamplesHubMainMenu.unity** scene has the cube buttons.
 
+## Prerequisite ##
+MRTK Examples Hub uses [Scene Transition Service](https://microsoft.github.io/MixedRealityToolkit-Unity/Documentation/Extensions/SceneTransitionService/SceneTransitionServiceOverview.html) and related scripts. If you are using MRTK through Unity packages, please import **Microsoft.MixedReality.Toolkit.Unity.Extensions.x.x.x.unitypackage** which is part of the [release packages](https://github.com/microsoft/MixedRealityToolkit-Unity/releases). If you are using MRTK through the repository clone, you should already have **MixedRealityToolkit.Extensions** folder in your project.
+
 ## MRTKExamplesHub Scene and the Scene System ##
 Open **MRTKExamplesHub.unity** which is located at ``MixedRealityToolkit.Examples/Demos/ExamplesHub/Scenes/`` It is an empty scene with MixedRealityToolkit, MixedRealityPlayspace and LoadHubOnStartup. This scene is configured to use MRTK's Scene System. Click ``MixedRealitySceneSystem`` under MixedRealityToolkit. It will display the Scene System's information in the Inspector panel.
 <br/><br/><img src="../Documentation/Images/ExamplesHub/MRTK_ExamplesHub_Hierarchy.png" width="300">