Merge pull request #671 from jackeyjia/patch-20

add type for each go and js code block

problems/二叉树理论基础.md

@@ -215,7 +215,7 @@ class TreeNode:
 ```
 
 Go：
-```
+```go
 type TreeNode struct {
     Val int
     Left *TreeNode
@@ -224,7 +224,7 @@ type TreeNode struct {
 ```
 
 JavaScript：
-```
+```javascript
 function TreeNode(val, left, right) {
     this.val = (val===undefined ? 0 : val)
     this.left = (left===undefined ? null : left)