Add release date

Author: JoseEspinosa

CHANGELOG.md

@@ -3,7 +3,7 @@
 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).
 
-## v2.1.0 - [date]
+## [[2.1.0](https://github.com/nf-core/chipseq/releases/tag/2.1.0)] - 2024-10-02
 
 ### Enhancements & fixes