Detect if the npm install was already done

[leodido]

Describe the feature or problem you’d like to solve

This CLI is meant to be used before installing any dependency, theoretically.

So, we should detect if the users already run npm install and warn them accordingly.

Doing this will - hopefully - raise awareness about the packages getting installed.

Proposed solution

Checking whether the node_modules and/or the package-lock.json already exists in the target directory should suffice.

Additional context

NONE

[leodido]

Do this after we have a fancy outputting mechanism in place.