[Issue #59] Set up cli/ codebase

[widal001]

Summary

Sets up the cli/ codebase and mocks the commands we expect to implement in future tickets.

• Fixes Set up the cli/ section of the codebase #59
• Time to review: 10 minutes

Changes proposed

What was added, updated, or removed in this PR.

• Creates and sets up the cli/ sub-package
• Creates a commander.js CLI application with a set of mock entry points
• Sets up linting, formatting, and a test suite

Context for reviewers

Testing instructions, background context, more in-depth details of the implementation, and anything else you'd like to call out or ask reviewers. Explain how the changes were verified.

1. Checkout the PR
2. Navigate to the cli/ codebase: cd cli
3. Run the build npm run build
4. Link the package locally: npm link
5. Run cg help for the help menu

Additional information

Screenshots, GIF demos, code examples or output to help show the changes working as expected.