code: async function lookup(words) {
    const index = new Index();
    const hits = await index.lookup(words);
    index.quit();
    words.forEach((word, i) => {
      console.log(`hits for "${word}":`, hits[i].join(', '));
    });
    return hits;
  }
docs: Given a list of words, lookup any matches in the database.
  @param {string[]} words
  @returns {Promise<string[][]>}