Add option to return matched detection events

[oscarhiggott]

Currently, Matching.decode returns the edges in the solution but not the detection events that have been paired up. It would be nice if the pairs of detection events could be returned, perhaps along with the observables crossed along the shortest path between them.

[oscarhiggott]

This is now fixed and will be in the next release. I added methods pymatching.Matching.decode_to_matched_dets_array and pymatching.Matching.decode_to_matched_dets_dict which return the pairs of detection events which are matched with paths in the solution (either as a two-column numpy array or as a dictionary).