Bump what's new.md

dist/preview release/what's new.md

@@ -80,6 +80,7 @@
 - Bumped Monaco Editor to 0.18.1 and improved TypeScript compilation pipeline in the playground ([sailro](http://www.github.com/sailro))
 - Added support for clickable errors in the playground ([sailro](http://www.github.com/sailro))
 - Added a color picker and previewer for BABYLON.ColorX invocations in the playground ([sailro](http://www.github.com/sailro))
+- Added support for diffing snippets in the playground ([sailro](http://www.github.com/sailro))
 
 ### Meshes