Add warning and error messages for the validation feature #36
Description
Improve the validation feature by adding human readable messages that explain what validation rules break the workflow.
It should act like a regular linter.
Current behavior
Putting validation_depth at more than 0 can break the workflow. Which is expected. But the end user doesn't know what is currently breaking the workflow.
Expected behavior
Display in the standard output the reason why a workflow is broken by this action.
Inspiration
Something like the other linter's output would be awesome:
