Update README.md

Co-authored-by: Raphael Schweikert <[email protected]>

Author: oliverklee

README.md

@@ -661,6 +661,7 @@ class Sabberworm\CSS\CSSList\Document#4 (2) {
 
 ## Contributors/Thanks to
 
+ * [oliverklee](https://github.com/oliverklee) for lots of refactorings, code modernizations and CI integrations
 * [raxbg](https://github.com/raxbg) for contributions to parse `calc`,
   grid lines, and various bugfixes.
 * [westonruter](https://github.com/westonruter) for bugfixes and improvements.