Update repo to better organize and document scope and targeted scenarios

[adriandiglio]

• Add a typical scenario of usage to illustrate the scope of this tool
• Improve dev experience of the repo so they can more easily know where and how to contribute
• Overall clean up of repo to better organize and document the effort

[xee5ch]

I think an important first step in moving forward with the work is to "apply" some of the information from the concept of operations diagram from NIST's BloSS@M Project, we may want to discuss the scope and targeted scenarios first and I can touch up the diagram.

To start, @adriandiglio, do we agree we should focus on the L1 maturity practices to form controls, discuss as a group how to prioritize those, and then consider the automation around each? I will try to build out a diagram and some notes in a PR. This work would be more around "how do we plan an OSCAL automation lifecycle" then another step which will focus on "ok, we will apply that lifecycle for S2C2F L1 practices" as a next step. Thoughts?