README.md in the root directory needs update

[iMichaela]

Describe the bug

The README.md file in the root directory lists the directory structure and descriptions of the src directory since it is a copy of the README.md from that directory.

- nist.gov/SP800-53/rev4: This directory contains OSCAL examples of the catalog, and low, moderate, and high baselines defined by NIST Special Publication (SP) 800-53 Revision 4.

- nist.gov/SP800-53/rev5: This directory contains OSCAL examples of the catalog, and low, moderate, and high baselines defined by NIST Special Publication (SP) 800-53B Revision 5 and SP 800-53B Revision 5 respectively.

- fedramp.gov: This directory contains OSCAL examples of the low, moderate, and high baselines defined by FedRAMP (the Federal Risk and Authorization Management Program).

- components: This directory contains sample OSCAL component files.

- mini-testing: This directory contains sample files that can be used for unit testing in support of regressions of OSCAL.

The structure of the root directory and content of README.md should list, in addition to the .github directory and the link to OSCAL schema repo, the following:

- components: This directory contains sample OSCAL component files.

- fedramp.gov: This directory contains OSCAL examples of the low, moderate, and high baselines defined by FedRAMP (the Federal Risk and Authorization Management Program).

- nist.gov/SP800-53/rev4: This directory contains OSCAL examples of the catalog, and low, moderate, and high baselines defined by NIST Special Publication (SP) 800-53 Revision 4.

- nist.gov/SP800-53/rev5: This directory contains OSCAL examples of the catalog, and low, moderate, and high baselines defined by NIST Special Publication (SP) 800-53B Revision 5 and SP 800-53B Revision 5 respectively.

- src: This directory contains the source files for all the OSCAL examples located in this repository.

- ssp-example: This directory contains the SSP data model and SSP mock-up samples

[david-waltermire]

This issue was addressed by the commit above.