Document instructions for running the obographs-compliance suite

@cmungall can you provide a page docs page on how to use the obographs compliance framework?

We are close to a robot release and we need this merged now:

https://github.com/ontodev/robot/pull/1198

The first in a two stage process towards some important obographs extensions.

Read the linked ROBOT PR #1198 first to understand the release context and intended compliance workflow. The task is done when a documentation page explains how to use the obographs-compliance framework; the issue does not identify a documentation file, command, or validation test.

Written by the indexing model from the issue text.