Should we require primary/secondary contact GitHub handle?

[domenic]

Currently we require it because we expect updates to the CWA to be done via pull request; see https://participate.whatwg.org/agreement-update. However, we could always accept update requests from the (provided) email.

Longer-term, we probably will have a nice web interface for updates, but even that will rely on GitHub authentication. (Unless we want to create our own username/password database, which seems unwise.)

I'm not sure if we should change this, but it's worth considering...