Update changelog

Author: adangel

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 * [#50](https://github.com/pmd/pmd-designer/pull/50) Usability improvements by [Juan](https://github.com/jsotuyod)
 
+See https://github.com/pmd/pmd-designer/milestone/14
+
 ## 6.28.0
 
 * **Bump required pmd-core version to 6.27.0.** The previous minimal pmd-core version was 6.23.0.