Case prioritization

[gmittal]

Given that our MVP is basically complete, it's worth thinking about some of the additional (and somewhat more open-ended) components of our system.

In our MVP release we are only prioritizing cases by timestamp. However, some cases are definitely more important than others. It would be nice to have a function in copilot-prioritize that sorts cases by other features, such as whether a case contains signs of suicidal language or if the demographics of the user put them especially at risk.