Add co-op entrance tracking

[kbranch]

From PoryGone:

there's a Pokemon Entrance Rando tracker that some people will use to essentially co-op solve an ER seed together

Seems like AP would make this pretty easy if they're all playing the same slot. Just set up an event listener for the found_entrances storage.

[kbranch]

AP does this now, debatable if it's worth implementing natively in Magpie.