Split CLI and API into separate packages

A more long-term idea: at some point it would be nice to have a monorepo with separate npm packages for the cli and the api. That way, heavier [dependencies](https://github.com/ipfs-shipyard/ipfs-deploy/issues/1#issuecomment-545534206) needed for better usability (say, [CLI React](https://github.com/vadimdemedes/ink)?) can be segregated to the cli, leaving a lean, tree-shakeable api for other types of integrations.