[documentreview] Document the process for handling review comments at transitions

[r12a]

From @nigelmegitt (originally at #276):

As a general point, as per w3c/process#130 it would be good to document the process for handling review comments, and what kinds of responses are likely to result in a transition request being declined.

For example, if a responder says "I don't like the colour of the text in this document" and the WG ignores the comment, not even sending a response, is that okay? Or at the other end of the scale, if a commenter raises a detailed technical point, the WG considers and responds, and then the commenter remains unhappy with that response, is that okay?

What level of tracking of responses is required and what is merely good practice?