* Update README
* Add info on Community channels (google group, chats)
* Restructure main section on background and core team
* Fix typos and add CODEOWNERS
* Rename CODEOWNERS to MAINTAINERS
This includes all team members, not just engineers, and we are already
tracking code owner engineers under .github/CODEOWNERS
* Add link to and explanation of CODEOWNERS
Co-authored-by: Shelby Switzer <shelby.switzer@cms.hhs.gov>
