Update CHANGELOG

Author: krassowski

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - bug fixes
   - improved performance of completion and highlights by minimising the number of highlight requests and GUI redraws (token checking, debouncing, acting on a single response only) ([#433])
+  - highlights now update after cell focus/blur events even if those do not trigger cursor movement ([#433])
 
 [#433]: https://github.com/krassowski/jupyterlab-lsp/issues/433