Update CHANGELOG.md

Author: vincentpierre

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [0.3.0-preview] - 2020-06-09
 
-###Description
+### Description
  - Updated the shared memory communication to be more modular
  - Added materials and textures to the 3DBall Sample
  - Modified the API to reflect changes made to mlagents_envs version 0.16.0