Summary: Fixes T6347. This refines the "contributor guide" documents to basically lock down support further. Notable changes in policy: - Bugs: Emphasis on reproduction steps, strong emphasis on using Maniphest. Emphasis on what we support. - Features: Emphasis on describing problems instead of solutions, emphasis on realistic expecations about timelines. Strong emphasis on using Maniphest. - Code: Strong emphasis on coordinating with us first. No GitHub pull requests. Emphasis on us ignoring contributions we don't have time to deal with. Suggests local forks. Test Plan: Read these through; let me generate them and take some screenshots for easier reading. Reviewers: btrahan, chad Reviewed By: chad Subscribers: epriestley Maniphest Tasks: T6347 Differential Revision: https://secure.phabricator.com/D10764