Add 6.2.0 to CHANGELOG

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 Note: I'm not mentioning the plethora of functions that I'm adding with every minor version bump. [Take a look at the full function list](https://github.com/grrr-amsterdam/garp-functional/tree/master/library/Garp/Functional). This changelog will only list breaking changes.
 
+## 6.2.0
+
+- Improve return types in PHPDoc
+- Add PHPstan badge to README
+- Code improvements
+
 ## 6.1.0
 
 - Add conditional return types in PHPDoc