ref(docs): rewrite coding standards doc as a PR checklist

The "coding standards" document needed an update for go, our
most prevalent implementation language. It was also verbose and
a bit rambling as it had grown over time, so this attempts
to condense and focus it as a simpler checklist to follow.
Merge pull request #2119 from mboersma/update-code-standards

ref(docs): rewrite coding standards doc as a PR checklist