Updated changelog for release 4.2.3

Author: bohdan-harniuk

CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0).
 
 ## 4.2.3
 
+### Fixed
+
+- Fixed a simple-json library is absent in the distribution in [#951](https://github.com/magento/magento2-phpstorm-plugin/pull/951)
+
 ## 4.2.2
 
 ### Added