adjust changelog

CHANGELOG.md

@@ -1,10 +1,18 @@
 # Changelog
+All notable changes to this project will be documented in this file.
 
-## 1.0.0.0 (2022-07-25)
+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).
 
+## [Unreleased]
+
+## [1.0.0.0] - 2022-07-25
 ### Added
 - performs POST forwarding in the following controllers
   - Search
   - Article lists (categories, manufacturers, vendors)
   - Contact
 - no forwarding in case of errors in the contact form
+
+[Unreleased]: https://git.d3data.de/D3Public/PRGredirect/compare/1.0.0.0...HEAD
+[1.0.0.0]: https://git.d3data.de/D3Public/PRGredirect/releases/tag/1.0.0.0