Define tests that are Drupal-best-practice specific

While core WCAG testing is good, there are several best practices that can be identified by the Drupal community that this module could test for. Examples might include:

• When using element-invisible to label a link, put the element inside the link, not just right next to it, so it's scannable in link lists.
• Appropriate use of element-invisible vs. element-hidden.

This issue can be a place to post ideas on what tests should be included, or whether this is a good idea ;)