Amendments on copyright for 0003: Guidelines on Licensing and DCO

[kim]

Changes the wording of copyright notices to read "The Contributors" in LICENSE files, and adds a rustfmt header check template which doesn't require a fixed copyright holder.

Reasoning: in the jurisdictions we're operating in, copyright is not transferrable. While contributions by employees fall under the copyright of the employer, this is not true for external contributions: if the work is copyrightable (ie. "substantial"), they can add their own name to the license header of the file(s) they created / modified.