Reorganize contributor documentation (flutter#23963)

CODE_OF_CONDUCT.md

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+# Code of conduct
+
+We expect Flutter's contributors to act professionally and respectfully, and
+we expect our social spaces to be safe and dignified environments.
+
+Specifically:
+
+* Respect people, their identities, their culture, and their work.
+* Be kind. Be courteous. Be welcoming.
+* Listen. Consider and acknowledge people's points before responding.
+
+Should you experience anything that makes you feel unwelcome in Flutter's
+community, please contact someone on the team, for instance
+[Ian](mailto:[email protected]) or [Tim](mailto:[email protected]). We will
+not tolerate harrasment from anyone in Flutter's community, even outside
+of Flutter's public communication channels.
+
+## Conflict resolution
+
+When multiple contributors disagree on the direction for a particular
+patch or the general direction of the project, the conflict should be
+resolved by communication. The people who disagree should get
+together, try to understand each other's points of view, and work to
+find a design that addresses everyone's concerns.
+
+This is usually sufficient to resolve issues. If you cannot come to an
+agreement, ask for the advice of a more senior member of the team.
+
+Be wary of agreement by attrition, where one person argues a point
+repeatedly until other participants give up in the interests of moving
+on. This is not conflict resolution, as it does not address everyone's
+concerns. Be wary of agreement by compromise, where two good competing
+solutions are merged into one mediocre solution. A conflict is
+addressed when the participants agree that the final solution is
+_better_ than all the conflicting proposals. Sometimes the solution is
+more work than either of the proposals. [Embrace the yak
+shave](https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#lazy-programming).
+
+## Questions
+
+It's always ok to ask questions. Our systems are large, nobody will be
+an expert in all the systems. Once you find the answer, document it in
+the first place you looked. That way, the next person will be brought
+up to speed even quicker.
+
+[!["I try not to make fun of people for admitting they don't know things, because for each thing 'everyone knows' by the time they're adults, every day there are, on average, 10,000 people in the US hearing about it for the first time. If I make fun of people, I train them not to tell me when they have those moments. And I miss out on the fun." "Diet coke and mentos thing? What's that?" "Oh man! We're going to the grocery store." "Why?" "You're one of today's lucky 10,000." (xkcd, May 2012)](https://imgs.xkcd.com/comics/ten_thousand.png)](https://xkcd.com/1053/https://xkcd.com/1053/)