[New Feature]: Add "high coherence" multi-reference point option #610
Description
As an alternative to the single-point, "middle of the largest connected component", we can add an option to use the median of all high coherence points.
This can be taken from https://github.com/opera-adt/opera-utils/blob/main/src/opera_utils/disp/_reference.py#L79-L81 (minus the xarray implementation)