Site should have property file example on the Testing page

It would be pretty easy for someone to create an app and want to unit test it w/o having digested all the AndHow docs / website. In that case, the Testing page doesn't include a sample of a properties file. Also, it would be nice to be able to include a link in the JUnit 5 annotations to what a properties file needs to look like.

Start with the Testing page and inspect the JUnit 5 annotations referenced there. Add a representative properties-file example and link the annotations to the required properties-file format; the documentation is done when readers can find both the example and the linked requirements.

Written by the indexing model from the issue text.