Option to omit parents from the output

[t49tran]

Hi @mwittig , thanks for the great tool, we use npm-license-crawler as part of our projects at work now to keep track of all direct dependencies.

One thing I observe is when run with --onlyDirectDependencies options, basically all package parents will be the same and is that of the main package. It's kind of redundant and unnecessary.

Are you open to an idea to introduce an option to omit the parents tag, or there has already been a way to remove it ?

I am happy to figure out how to do it and submit a PR if it's required.