Update what's new.md

dist/preview release/what's new.md

@@ -15,7 +15,8 @@
  - `Mesh.applyDisplacementMap` now accepts uvScale and uvOffset parameter ([deltakosh](https://github.com/deltakosh))
  - Added addChild, removeChild, setParent to AbstractMesh ([abow](https://github.com/abow))
  - `Effect.getVertexShaderSource()` and `Effect.getFragmentShaderSource()` now returns the effective shader code (including evaluation of #define) ([deltakosh](https://github.com/deltakosh))
-
+ - GroundMesh : `getHeightAtCoordinates()`, `getNormalAtCoordinates()` and `getNormalAtCoordinatesToRef()` can now work with rotated grounds ([jerome](https://github.com/jbousquie))  
+ 
 ### Canvas2D
 
 #### Major Updates