Document current maintainers

[nimbinatus]

Document complete list of current maintainers, including names, contact information, domain of responsibility, and affiliation.

This really is just making sure our MAINTAINERS.md is up to date with all of the right information. Should be a check of what we've already done.

Also

A number of active maintainers which is appropriate to the size and scope of the project.

This should be a given, but check the list while we're there.