Top Level Links to Registry and Knowledge Base

[brian-comply0]

Description

As a visitor to the web site I want know how to find the Content Registry and the Knowledge Base (KB), so that I can easy navigate to those capabilities.

Acceptance Critiera

• [ ] Link at the top of page for:
  • [x] "Content Registry" (points to registry.oscal.io)
  • [x] "Knowledge Base" (points to docs.oscal.io)
  • [x] A brief section on the main page about the OSCAL Content Registry

Additional Notes

No response

[cdroblee]

@pjavan @brian-comply0 let's use this one