Add API to retrieve status of reviews

[jdm]

It would be really great to integrate tools like https://github.com/peterbe/github-pr-triage with Critic for projects like Servo. However, there doesn't seem to be any kind of API to retrieve the current status of a review (eg. how much is unreviewed, who is needed to perform said reviews, etc.).

[jensl]

There is no such API, no. There is a very early draft implementation of a JSON API in review (https://critic-review.org/r/197) but I don't see myself working more on that any time soon.

It is on the other hand entirely possible to write a simple Critic extension that adds an API exposing whatever information you like (that is available through the extension API.) Unfortunately, I don't think the extension API does expose the "who needs to review" today but that would be easy to add.