Update what's new.md

dist/preview release/what's new.md

@@ -61,6 +61,7 @@
     - Fixed a possible but with the active camera while taking a screenshot. [PR](https://github.com/BabylonJS/Babylon.js/pull/701) ([RaananW](https://github.com/RaananW))
     - Fixed a bug with worker-collisions and instances. [PR](https://github.com/BabylonJS/Babylon.js/pull/705) ([RaananW](https://github.com/RaananW))
     - Fixed a bug with removed meshes and geometries from the worker-cache. [PR](https://github.com/BabylonJS/Babylon.js/pull/711) ([RaananW](https://github.com/RaananW))
+    - Fixed `getHeightAtCoordinates()` : brand new ultra fast algorithm, can be used for many objects at once in the render loop now ([jerome](https://github.com/jbousquie))
     - Fixed `closePath` and `closeArray` ribbon parameter now working back together ([jerome](https://github.com/jbousquie))
     - Fixed morphing on capped tubes  ([jerome](https://github.com/jbousquie))
     - Fixed morphing on extruded shapes  ([jerome](https://github.com/jbousquie))