code: function isKyouikuKanji(ch) {
      return includes(kyouikuKanji.grade1, ch) ||
      includes(kyouikuKanji.grade2, ch) ||
      includes(kyouikuKanji.grade3, ch) ||
      includes(kyouikuKanji.grade4, ch) ||
      includes(kyouikuKanji.grade5, ch) ||
      includes(kyouikuKanji.grade6, ch);
  }
docs: determine whether a character is a kyouiku kanji character