Add process for PR acceptance, review, rejection

This is an extremely tentative PR.  However, I feel that the suggestions are generally good.

Docker-DCO-1.1-Signed-off-by: Timothy Hobbs <timothyhobbs@seznam.cz> (github: timthelion)
I'd suggest a time frame for this - I often ask for further docs to help the submitter explain better what their PR addresses - which should also help the core team review faster, but at some point, without that info, the project should probably stop guessing.