Update CHANGELOG.md

Author: Fab1n

CHANGELOG.md

@@ -13,6 +13,10 @@
 
 ## Master
 
+## 3.21.2
+
+- Fix Runner's path resolution to enable `--cwd` with relative paths [@Fab1n][] - [#650](https://github.com/danger/swift/pull/650)
+
 ## 3.21.1
 
 - Fix current directory url creation [@f-meloni][] - [#640](https://github.com/danger/swift/pull/640)