code: function createChoiceUl () {
    const lis = story.currentChoices
      .map(choice => {
        const li = document.createElement('li');
        li.innerHTML = choice.text;
        createChoiceListener(li, choice.index);
        return li;
      });
    const ul = document.createElement('ul');
    Array.from(lis).forEach(li => ul.appendChild(li));
    ul.className = "choices current";
    return ul;
  }
docs: Create the ul element that contains a batch of choices.