----------------------------------------------------------------------------- Char NFA fragment: `c` 
Char factory.

Creates an NFA fragment for a single char.

[in] --c--> [out]
function char(c) {
  const inState = new NFAState();
  const outState = new NFAState({
    accepting: true,
  });

  return new NFA(inState.addTransition(c, outState), outState);
}