Updated what's new

dist/preview release/what's new.md

@@ -151,6 +151,7 @@
 - Fixed issue where gaze trackers were appearing even after leaving VR ([atulyar](https://github.com/atulyar))
 - AdvancedDynamicTexture should not overwrite skipOnPointerObservable to false ([TrevorDev](https://github.com/TrevorDev))
 - Fixed issue where VRExperienceHelper.onExitingVR observable was being fired twice ([atulyar](https://github.com/atulyar))
+- Avoid firing onExitingVR observable multiple times when calling exitVR() and add observables to Viewer that can be used instead of the ones in VRExperienceHelper ([atulyar](https://github.com/atulyar))
 
 ### Core Engine