code: function toKatakana(input = '', options = {}) {
    const config = Object.assign({}, DEFAULT_OPTIONS, options);
    if (config.passRomaji) return hiraganaToKatakana(input);
    if (isRomaji(input) || isMixed(input)) {
      const romaji = romajiToHiragana(input, config);
      return hiraganaToKatakana(romaji);
    }
    return hiraganaToKatakana(input);
  }
docs: Convert input to [Katakana](https://en.wikipedia.org/wiki/Katakana)
  @param  {String} [input=''] text
  @param  {DefaultOptions} [options=defaultOptions]
  @return {String} converted text
  @example
  toKatakana('toukyou, おおさか')
  // => 'トウキョウ、　オオサカ'
  toKatakana('only かな', { passRomaji: true })
  // => 'only カナ'
  toKatakana('wi')
  // => 'うぃ'
  toKatakana('wi', { useObsoleteKana: true })
  // => 'ヰ'