Document how to recognize and correct for false-positive and false-negatives

[davemasselink]

The concept of a health check succeeding or failing is related to the final return value from the nested/imported Argo workflow.

This isn't always incredibly obvious and can lead to scenarios where the workflow doesn't behave as expected yet is still marked as succeeded. Similarly, even if the workflow behaves as expected, it may indicate a failure if a non-0 return code is used.

README documentation should be improved to highlight this and provide users with patterns/strategies to ensure that healthchecks are behaving as expected and building confidence in the usage of Active-Monitor.