docs: add changelog entry

Author: DannyvdSluijs

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Welcome first time contributors ([#782](https://github.com/jsonrainbow/json-schema/pull/782))
 
+### Fixed
+- Upgrade php cs fixer to latest ([#783](https://github.com/jsonrainbow/json-schema/pull/783))
+
 ### Changed
 - Used PHPStan's int-mask-of<T> type where applicable ([#779](https://github.com/jsonrainbow/json-schema/pull/779))
 - Fixed some PHPStan errors ([#781](https://github.com/jsonrainbow/json-schema/pull/781))