Adding a Code of Conduct to MacPorts

[Vincent Habchi]

> In my experience, we in MacPorts-land don't have the obvious Linux issue. I hope others don't experience the MacPorts project (developers, users, commenters) as abusive in any medium (email lists, tickets / issues, PR's, in person, whatever). - MLD

In my experience :), when a project feels the necessity to adopt a code of conduct, that means it is on the verge of capsizing. Between people of good will, there is no need for such a thing: good behavior is just common sense.

Vincent