Establish a membership/registration mechanism

[EiffL]

As we have proposed in #1 , to become a member, one would have to explicitly agree to the terms of the collaboration. One we have a enacted these terms, we might want a mechanism for people to register as members of the initiative.

A simple mechanism would be to have an issue template in this repo, that people can click and complete. That issue template would simply be saying something like: "I accept the terms ...." and one maintainer would then add that person to the github team "member".