snapshot method

@override Map<String, Object?>? snapshot()

Override to return a snapshot of your state's fields.

Used by:

1. Orbit.observe/Orbit.changeLog to report exactly what changed on each mutation.
2. Stores mixing in Undoable to record state history for Orbit.undo / Orbit.redo.

Implementation

@override
Map<String, Object?>? snapshot() {
  return {
    'state': _state,
  };
}