create utility functions for lint rule authors to test their rules

[ivanhofer]

Authors should check if the rule or collection returns an object with the required structure and if they correctly handle the configuration passed to a rule. Becasue this needs to be done for all repositories, creating some utility functions would benefit all authors.

Maybe creating a template repository makes sense.
The template would contain a simple rule and collection with some basic test setup. This template can then be extended in a few steps.
An author would only need to change the implemantation and add some tests. Tooling setup, packaging etc. would already be present.