Updated DEPLOYMENT (markdown)

DEPLOYMENT.md

@@ -21,3 +21,4 @@ Follow this steps to deploy a new version of Rambox:
 11. Publish release in Github.
 11. Go to **Heroku** instance and in Resources tab, disable Dynos and enable it again (if no version detected yet, we have to force it).
 12. Go to **Firebase** and update with the new version to notify users.
+13. Publish message in social networks mentioning new services and send emails.