code: function checkImportant(i) {
    const start = i;
    let l;
  
    if (i >= tokensLength ||
        tokens[i++].type !== TokenType.ExclamationMark) return 0;
  
    if (l = checkSC(i)) i += l;
  
    if (tokens[i].value === 'important') {
      tokens[start].importantEnd = i;
      return i - start + 1;
    } else {
      return 0;
    }
  }
docs: Check if token is part of `!important` word
  @param {number} i Token's index number
  @return {number}