[package shallow] Add replacement for info command

[pvdz]

This adds a new command: socket package shallow, which is in the same vain as the socket info command except it doesn't reflect the dependencies or its transitives.

• It uses the /purl endpoint, rather than the /npm endpoint
• It supports looking up multiple packages at once
• It supports a list of purls and npm babel tenko sort of args and even a mix
• Supports --json --markdown or neither

$ socket package shallow npm socket@latest tenko babel-cli@^6.26

$ socket package shallow npm socket@latest tenko babel-cli@^6.26 --markdown

$ socket package shallow npm socket@latest tenko babel-cli@^6.26 --json