An RFC for governance of the Rust project

The Rust community has been working to reform its governance model; thatwork is now being presented as adraft document describing how that model will work.

This RFC establishes a Leadership Council as the successor of thecore team and the new governance structure through which RustProject members collectively confer the authority to ensuresuccessful operation of the Project. The Leadership Councildelegates much of this authority to teams (which includes subteams,working groups, etc.) who autonomously make decisions concerningtheir purviews. However, the Council retains some decision-makingauthority, outlined and delimited by this RFC.