Version in the changelog

Signed-off-by: Fabio José <[email protected]>

Author: fabiojose

CHANGELOG.md

@@ -4,8 +4,10 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
-## [Unreleased]
+## [0.3.1]
+
 ### Fixed
+
 - Axios version to `0.18.1` due the CVE-2019-10742
 - Fix the `subject` attribute unmarshal error: issue
 [#32](https://github.com/cloudevents/sdk-javascript/issues/32)