Update README.md

Geekhyt · web-flow · commit 32a6e265c312 · 2021-02-02T20:20:13.000+08:00
diff --git a/README.md b/README.md
@@ -27,3 +27,4 @@
 - [145. 二叉树的后序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/15)
 - [100. 相同的树](https://github.com/Geekhyt/javascript-leetcode/issues/16)
 - [101. 对称二叉树](https://github.com/Geekhyt/javascript-leetcode/issues/17)
+- [102. 二叉树的层序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/18)
