Library of predefined CliCommands

It would be nice to have a library of CliCommands that are maintained as a project within itself so that each developer doesn't have to come a long and write up all the boilerplate code each time they want to parse a command line.

A bit like types for TypeScript, the cli commands would then be used to parse commands for well-known command line tools such as Node.js.

Node.js has a comprehensive set of options, and to fully parse a Node.js command would take a mammoth amount of work, but it isn't just Node.js, there are many other libraries where it would take a long time to write all the code required to properly understand the command.

I am not proposing we do this as part of the [command-line-api](https://github.com/dotnet/command-line-api) project, I am proposing another project that can be used alongside this that will provide some useful definitions for developers.