Update README.md

Geekhyt · web-flow · commit 22a028be672b · 2021-02-26T15:48:48.000+08:00
diff --git a/README.md b/README.md
@@ -62,6 +62,7 @@
 - [冒泡排序](https://github.com/Geekhyt/javascript-leetcode/issues/39)
 - [插入排序](https://github.com/Geekhyt/javascript-leetcode/issues/40)
 - [选择排序](https://github.com/Geekhyt/javascript-leetcode/issues/41)
+- [归并排序](https://github.com/Geekhyt/javascript-leetcode/issues/42)
 
 ## 动态规划
 - [70. 爬楼梯](https://github.com/Geekhyt/javascript-leetcode/issues/38)
