Add TestFlight Release Notes/What To Test to Deploy to Bitrise step

It would be helpful to be able to add Release Notes/What To Test to the Deploy to Bitrise step.

This would allow for teams to be notified of what type of release it is (dev/qa/prod) as well as what to test. Some services like AppCenter also allow you to specify a release type which would further be helpful.

We can add last commit message to release note.