docs: link to GitHub releases

Author: spawnia

CHANGELOG.md

@@ -5,6 +5,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+See [GitHub releases](https://github.com/mll-lab/php-utils/releases).
+
 ## Unreleased
 
 ## v1.3.0