Adding a third status to the compat table matrix

[jasnell]

Describe the feature

Right now results are either green or red. Several of the APIs in the table are intentionally not implemented by runtimes -- for instance, workerd does not plan on implementing BroadcastChannel any time soon. In other cases, the API may be implemented but have caveats associated with it. It would be nice if runtimes could essentially report a third status for an API that allows the runtime to specify a comment/note like "This API is not applicable", etc

Additional information

• Would you be willing to help implement this feature?

[ascorbic]

I'm not sure how this could be maintained, as the other results are all auto-generated. Maybe a manually-maintained file of notes that can be applied against certain tests