add readme

@@ -16,7 +16,7 @@ leetcode-cn.com上的题库代码实现
 |                             | 10    | [正则表达式匹配](https://leetcode-cn.com/problems/regular-expression-matching) | **困难** |
 |                             | 11    | [盛最多水的容器](https://leetcode-cn.com/problems/container-with-most-water) | **中等** |
 |                             | 12    | [整数转罗马数字](https://leetcode-cn.com/problems/integer-to-roman) | **中等** |
-|                             | 13    | [罗马数字转整数](https://leetcode-cn.com/problems/roman-to-integer) | **简单** |
+| 13-romanToInt.js | 13    | [罗马数字转整数](https://leetcode-cn.com/problems/roman-to-integer) | **简单** |
 |                             | 14    | [最长公共前缀](https://leetcode-cn.com/problems/longest-common-prefix) | **简单** |
 |                             | 15    | [三数之和](https://leetcode-cn.com/problems/3sum)            | **中等** |
 |                             | 16    | [最接近的三数之和](https://leetcode-cn.com/problems/3sum-closest) | **中等** |