feat: add Swift codes for binary_tree article

codes/swift/chapter_tree/binary_tree.swift

@@ -0,0 +1,40 @@
+/**
+ * File: binary_tree.swift
+ * Created Time: 2023-01-18
+ * Author: nuomi1 (nuomi1@qq.com)
+ */
+
+import utils
+
+@main
+enum BinaryTree {
+    /* Driver Code */
+    static func main() {
+        /* 初始化二叉树 */
+        // 初始化结点
+        let n1 = TreeNode(x: 1)
+        let n2 = TreeNode(x: 2)
+        let n3 = TreeNode(x: 3)
+        let n4 = TreeNode(x: 4)
+        let n5 = TreeNode(x: 5)
+        // 构建引用指向（即指针）
+        n1.left = n2
+        n1.right = n3
+        n2.left = n4
+        n2.right = n5
+        print("\n初始化二叉树\n")
+        PrintUtil.printTree(root: n1)
+
+        /* 插入与删除结点 */
+        let P = TreeNode(x: 0)
+        // 在 n1 -> n2 中间插入结点 P
+        n1.left = P
+        P.left = n2
+        print("\n插入结点 P 后\n")
+        PrintUtil.printTree(root: n1)
+        // 删除结点 P
+        n1.left = n2
+        print("\n删除结点 P 后\n")
+        PrintUtil.printTree(root: n1)
+    }
+}