update CHANGELOG file

Juanpe Catalán · Juanpe Catalán · commit 43c1c4266c65 · 2020-02-13T18:48:31.000+01:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -12,6 +12,7 @@
 -->
 
 ## Master
+- Adds mergeable state property in the Github PR struct [@Juanpe][] - [#318](https://github.com/danger/swift/pull/318)
 
 ## 3.1.0
 
