Update what's new.md

dist/preview release/what's new.md

@@ -3,7 +3,7 @@
     - New `StandardMaterial.lightmapTexture` which can be controlled with `StandardMaterial.lightmapThreshold`. [Demo here](#NEEDDEMO) ([deltakosh](https://github.com/deltakosh))
   - **Updates**
     - New `Material.sideOrientation` property to define clockwise or counter-clockwise faces selection. [Demo here](http://www.babylonjs-playground.com/#1TZJQY) ([deltakosh](https://github.com/deltakosh))
-    - It is now possible to create a custom loading screen ([RaananW](https://github.com/RaananW))
+    - It is now possible to create a custom loading screen [PR](https://github.com/BabylonJS/Babylon.js/pull/700) ([RaananW](https://github.com/RaananW))
   - **Bug fixes**
     - Fixed bug with texture coordinates matrices ([deltakosh](https://github.com/deltakosh))
     - Fixed Sphere texture coordinates generation ([deltakosh](https://github.com/deltakosh))