title: How to setup a development stage in my heroku pipeline
body: <p>A default heroku pipeline has the stages <code>review--&gt;staging--&gt;production</code>
  with <code>review</code> being optional.
  There is a way to add a <code>development</code> stage - but I can't find how to do this anywhere.</p>
  
  <p>Is there a way to do this through a config file in the repo, or CLI, or the web GUI?</p>