New rule: package.json validation for NodeJS about repolinter

[hyandell]

I was pondering whether it would be nice to implement this by having an axiom for 'build system' or 'package manager'. Then you could do:

package-manager=npm -> add the above rules using existing rule language

[hyandell]

packager axiom implemented. Need to PR.

[hyandell]

See #105

[Brend-Smits]

Closing this as I believe by adding Axiom support, this is all possible with the existing rules. If I'm mistaken, please do let me know, and I will re-open and clarify the issue description.