API design improvement ideas

- [ ] Using `InstanceReporter::par_check` should still produce an iterator, not a `Report` directly
- [ ] It should be easy to test a single word list at multiple instances, maybe add some abstraction over a collection of `InstanceReporter`s?
- Could this be lazy and/or capped somehow? Could help with memory usage on monster fonts
- [ ] Support collecting a `WordExtremesIter` into a `Report` (another extension trait similar to `CollectToExemplars`)
- This shouldn't have to take any report fields again, it should be cheap & easy for the iterator just store the references to what it'll need
- [x] Convenience method for creating an `InstanceReporter` at the default location
- [ ] Convenience method to create an `InstanceReporter` from a static font directly