Add FHIR Foundation Project Statement to README

[KaelynJefferson]

This PR includes:

• Updating the README.md with the "FHIR Foundation Project Statement" section that includes information about: Maintainers, Issues/Discussion, License, Contribution Policy, Security Information, and Compliance Information.
• The sections include links to relevant documents or resources.

[jafeltra]

This looks good to me!

If we think of it, we can edit the commit message when we merge to remove the portions that have commit messages from commits that weren't a part of this PR. If we don't think of it, not a big deal.

[cmoesel]

Perfect. Thanks, Kaelyn!