Establish workflow for Python Reference Doc edits

[jbogarthyde]

• [ ] Fix Edit the Doc button. The generated reference documentation for the Python Reference Implementation includes an Edit the Doc button. Currently, the button points directly to the source files. Change the button action to point to the contribution policy.
• [ ] Provide instructions for editors.
  Update contribution policy to add specific information about where the source code is found and who can review and approve changes to reference docs.