Add documentation explaining use of a component definition in an SSP

[david-waltermire]

User Story:

As an OSCAL user, I need to understand how a component in an OSCAL component definition can be used in an OSCAL SSP.

The content on the OSCAL website is a bit sparse on this topic.

Goals:

Need to build a diagram similar to the one produced by @dannamite.

Dependencies:

None.

Acceptance Criteria

• [ ] All OSCAL website and readme documentation affected by the changes in this issue have been updated. Changes to the OSCAL website can be made in the docs/content directory of your branch.
• [ ] A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• [ ] The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

{The items above are general acceptance criteria for all User Stories. Please describe anything else that must be completed for this issue to be considered resolved.}

[aj-stein-nist]

Marking this as blocked until #1910 is completed, and then it will be ready for "Needs Refinement" and determination if we edit this issue or replace it with a different one.