Update README.md

Author: scarsu

README.md

@@ -39,7 +39,7 @@
 
 - [20. 有效的括号](https://github.com/Geekhyt/javascript-leetcode/issues/21)✅
 - [84. 柱状图中最大的矩形](https://github.com/Geekhyt/javascript-leetcode/issues/22)✅
-- [155. 最小栈](https://github.com/Geekhyt/javascript-leetcode/issues/23)
+- [155. 最小栈](https://github.com/Geekhyt/javascript-leetcode/issues/23)✅
 
 ## 贪心