Update README.md

Geekhyt · web-flow · commit 99291a2f0391 · 2021-02-02T00:45:44.000+08:00
diff --git a/README.md b/README.md
@@ -23,3 +23,4 @@
 ## 树
 
 - [94. 二叉树的中序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/13)
+- [144. 二叉树的前序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/14)

Original file line number	Diff line number	Diff line change
`@@ -23,3 +23,4 @@`
`23`	`23`	`## 树`
`24`	`24`
`25`	`25`	`- [94. 二叉树的中序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/13)`
	`26`	`+- [144. 二叉树的前序遍历](https://github.com/Geekhyt/javascript-leetcode/issues/14)`