Updated release notes for XR renderscale and Shadow optimizaiton PRs.

com.unity.render-pipelines.lightweight/CHANGELOG.md

 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- pipeline now uses XRSEttings.eyeTextureResolutionScale as renderScale when in XR 
+
+### Changed
+- Screenspace shadow resolve is not only done when rendering shadow cascades
+
 ### Fixed
 - Fixed UnityPerDraw CB layout
 - GLCore compute buffer compiler error