Update changelog

Author: MariusKnirk

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](http://keepachangelog.com/) and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## 5.3.0 - 2025-08-28
+
+### Added
+- Support the latest version of the Oh Dear API and PHP SDK.
+
 ## 5.2.3 - 2025-06-02
 
 ### Fixed