feat: add ts solution to lc problem: No.701 (doocs#2833)

Author: rain84

solution/0700-0799/0701.Insert into a Binary Search Tree/README.md

@@ -177,6 +177,33 @@ func insertIntoBST(root *TreeNode, val int) *TreeNode {
 }
 ```
 
+#### TypeScript
+
+```ts
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function insertIntoBST(root: TreeNode | null, val: number): TreeNode | null {
+    if (!root) return new TreeNode(val);
+
+    if (val < root.val) root.left = insertIntoBST(root.left, val);
+    else root.right = insertIntoBST(root.right, val);
+
+    return root;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0700-0799/0701.Insert into a Binary Search Tree/README_EN.md

@@ -175,6 +175,33 @@ func insertIntoBST(root *TreeNode, val int) *TreeNode {
 }
 ```
 
+#### TypeScript
+
+```ts
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function insertIntoBST(root: TreeNode | null, val: number): TreeNode | null {
+    if (!root) return new TreeNode(val);
+
+    if (val < root.val) root.left = insertIntoBST(root.left, val);
+    else root.right = insertIntoBST(root.right, val);
+
+    return root;
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/0700-0799/0701.Insert into a Binary Search Tree/Solution.ts

@@ -0,0 +1,22 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function insertIntoBST(root: TreeNode | null, val: number): TreeNode | null {
+    if (!root) return new TreeNode(val);
+
+    if (val < root.val) root.left = insertIntoBST(root.left, val);
+    else root.right = insertIntoBST(root.right, val);
+
+    return root;
+}