code: func makeCharRange(min, max int) *Automaton {
  	if min > max {
  		return MakeEmpty()
  	}
  
  	a := newEmptyAutomaton()
  	s1 := a.createState()
  	s2 := a.createState()
  	a.setAccept(s2, true)
  	a.addTransitionRange(s1, s2, min, max)
  	a.finishState()
  	return a
  }
docs: /*
  Returns a new (deterministic) automaton that accepts a single rune
  whose value is in the given interval (including both end points)
  */