[TASK] Add kudos to @ziegenberg to the changelog (#583)

Author: oliverklee

CHANGELOG.md

@@ -35,6 +35,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 - Fix PHP notice caused by parsing invalid color values having less than 6 characters (#485)
 - Fix (regression) failure to parse at-rules with strict parsing (#456)
 
+@ziegenberg is a new contributor to this release and did a lot of the heavy
+lifting. Thanks! :heart:
+
 ## 8.5.0
 
 ### Added

README.md

@@ -793,6 +793,7 @@ classDiagram
 * [nicolopignatelli](https://github.com/nicolopignatelli) for PSR-0 compatibility.
 * [diegoembarcadero](https://github.com/diegoembarcadero) for keyframe at-rule parsing.
 * [goetas](https://github.com/goetas) for @namespace at-rule support.
+* [ziegenberg](https://github.com/ziegenberg) for general housekeeping and cleanup.
 * [View full list](https://github.com/sabberworm/PHP-CSS-Parser/contributors)
 
 ## Misc