Update what's new.md

dist/preview release/what's new.md

@@ -46,6 +46,9 @@
 ### WebXR
 - Added optional ray and mesh selection predicates to `WebXRControllerPointerSelection` ([Exolun](https://github.com/Exolun))
 
+### Collisions
+- Added an option to optimize collision detection performance ([jsdream](https://github.com/jsdream)) - [PR](https://github.com/BabylonJS/Babylon.js/pull/7810)
+
 ## Bugs
 
 - Fix infinite loop in `GlowLayer.unReferenceMeshFromUsingItsOwnMaterial` ([Popov72](https://github.com/Popov72)