Create a top level overview page documenting all the repos in the organization

[mrgadgil]

Issue description / feature objectives

Add a top level page at https://oscal-compass.github.io/ that describes the overall oscal-compass project and points at the various sub repos, rather than having it 404

Caveats / Assumptions

Completion Criteria

[jpower432]

@mrgadgil Can I transfer this issue to https://github.com/oscal-compass/oscal-compass.github.io and we can discuss more details on content?