Not sure if "adding unit or functional tests" makes sense. Took it from webpack example.

Also added your hierarchy of helpfulness under ### special note on issues. Don't know if the sentence introducing them is the best advice...

Also check the plugin naming convention.

Hope I'm getting the header levels right here.

There is some overlap here with the Gatsby style guide. I've got it on a to-do list to think through division of information between the two docs