feat: add Swift codes for heap article (#306)

* feat: add Swift codes for heap article

* Update heap.md

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/swift/utils/PrintUtil.swift

@@ -74,4 +74,12 @@ public enum PrintUtil {
             print("\(key) -> \(value)")
         }
     }
+
+    public static func printHeap(queue: [Int]) {
+        print("堆的数组表示：", terminator: "")
+        print(queue)
+        print("堆的树状表示：")
+        let root = TreeNode.listToTree(list: queue)
+        printTree(root: root)
+    }
 }