update what's new

dist/preview release/what's new.md

@@ -17,6 +17,7 @@
 - Added support for Particle animation in ParticleSystem ([Ibraheem Osama](https://github.com/IbraheemOsama))
 
 ## Updates
+- New observables for actions: `onBeforeExecuteObservable` for all actions and `onInterpolationDoneObservable` for `InterpolateValueAction` ([deltakosh](https://github.com/deltakosh))
 - New observables for gamepads: `onButtonDownObservable`, `onButtonUpObservable`, `onPadDownObservable`, `onPadUpObservable` ([deltakosh](https://github.com/deltakosh))
 - New `camera.storeState()` and `camera.restoreState()` functions to store / restore cameras position / rotation / fov. (Doc here)[http://doc.babylonjs.com/tutorials/cameras#state] ([deltakosh](https://github.com/deltakosh))
 - POW2 textures rescale is now done by shaders (It was previously done using canvas) ([deltakosh](https://github.com/deltakosh))