Add a release checklist as a RST document.
Add a release checklist as a RST document.

jamesblissett/PythonEditor,jamesblissett/PythonEditor,bbcmicrobit/PythonEditor,jamesblissett/PythonEditor,bbcmicrobit/PythonEditor,bbcmicrobit/PythonEditor,bbcmicrobit/PythonEditor