Add flags for what's new

dist/preview release/what's new.md

@@ -1,6 +1,8 @@
 # 3.1.0:
 
 ## Major updates
+- Viewer (TODO)
+- EnvironmentHelper + BackgroundMaterial (TODO)
 - Added support for webgl context lost and restored events. [Doc here](http://doc.babylonjs.com/tutorials/optimizing_your_scene#handling-webgl-context-lost) ([deltakosh](https://github.com/deltakosh))
 - Added support for non-pow2 textures when in WebGL2 mode ([deltakosh](https://github.com/deltakosh))
 - Engine can now be initialized with an existing webgl context ([deltakosh](https://github.com/deltakosh))