message: CHANGELOG: add v1.3.1 changes
diff: +## v1.3.1
  + - allowed calling `draggable.unset()` during `dragend` and `drop` event
  + listeners ([issue #560](https://github.com/taye/interact.js/issues/560))
  + - allowed snap to be enabled with falsey targets value [issue
  + #562](https://github.com/taye/interact.js/issues/562)
  +
  ## v1.3.0
  Most notably:
  