Add Unity VR Documentation

Add the official Unity 3D documentation for creating/developing virtual reality applications.

Author: mAzurkovic

README.md

@@ -134,6 +134,7 @@ A list of awesome projects made using Unity.
 * [Modern GUI Development in Unity 4.6](https://www.youtube.com/playlist?list=PLt_Y3Hw1v3QTEbh8fQV1DUOUIh9nF0k6c) - A video tutorial providing an in-depth explanation of Unity's new UI system. 
 * [Official Video Tutorials](http://unity3d.com/learn/tutorials/modules) - The official tutorials for scripting, animation, audio, and almost anything Unity related.
 * [Ray Wenderlich's Tutorials](http://www.raywenderlich.com/category/unity) - Beginner and mid-level tutorials focused on learning Unity features or creating small example games.
+* [Unity Virtual Reality](http://docs.unity3d.com/Manual/VROverview.html) - Unity's official documentation on developing virtual reality applications.
 
 # Contributing
 Please see [CONTRIBUTING](https://github.com/RyanNielson/awesome-unity/blob/master/CONTRIBUTING.md) for details.