JWK: Updated CHANGELOG

Author: bellebaum

CHANGELOG.md

@@ -4,6 +4,7 @@
 **Features:**
 
 - Support custom algorithms by passing algorithm objects[#512](https://github.com/jwt/ruby-jwt/pull/512) ([@anakinj](https://github.com/anakinj)).
+- Support descriptive (not key related) JWK parameters[#520](https://github.com/jwt/ruby-jwt/pull/520) ([@bellebaum](https://github.com/bellebaum)).
 - Your contribution here
 
 **Fixes and enhancements:**