Add contribution guidelines. These just link to the CoreCLR ones. Add
stubs of the "user guide" and "developer guide".
Add links to the Docker base image repo on GitHub.
Add README.md files with the contents of the "man pages" per directory that
implements all or part of the command. This way, we will enable easier
perusal of our repo as well as have an initial set of documentation published.
Add "documentation" directory as well for future work.