Add release version to changelog

Author: szhajdu

CHANGELOG-4.0.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [4.2.0] - 2024-03-15
 ### Added
 - PHP 8.3 support
 - codeception/lib-innerbrowser ^4.0 support