parseWS(ch) {
    if (/[ \t]/.test(ch)) {
      if (!this.mono) {
        this.spacing = true;
      } else {
        this.add(ch);
      }
      return true;
    }

    return false;
  }
Handle parsing of whitespace
@param {string} ch  the character to check
@returns {boolean} true if the character was processed as whitespace, false otherwise