Revisit workspace setup

[nkgentile]

It definitely makes sense to use a monorepo approach here, but the implementation is slightly confusing for new contributors.

• [ ] There is an unused package-lock.json file; consider deleting.
• [ ] Decide which package manager to use–either will suit this setup.
• [ ] Add top-level build script to help get new contributors up-and-running quicker
• [ ] Flesh out the README.md with some tips to get started