update what's new

dist/preview release/what's new.md

@@ -42,6 +42,7 @@
   - Prevented code from doing useless and possible time consuming computation when disposing the `ShaderMaterial` of a `LinesMesh`
   - Make a better use of the `isIdentity` cached value wihtin a `Matrix`
   - Make sure we browse all the submeshes only once in `Material.markAsDirty` function
+  - Added an `Vector3.UnprojectRayToRef` static function to avoid computing and inverting the projection matrix twice when updating a Ray.
 - Align `BoundingBox` and `BoundingSphere` API and behavior for clarity and simplicity. As a consequence, the `BoundingBox`'s method `setWorldMatrix` has been removed and the underlying world matrix cannot be modified but by calling `reConstruct` or `update`. ([barroij](https://github.com/barroij))
 - Make sure that `Material.markAsDirty` and all the `markXXXDirty` methods early out when `scene.blockMaterialDirtyMechanism` is true. ([barroij](https://github.com/barroij))