add avl tree and heap part cpp code (#320)

* 将avl_tree翻译成c++代码（文档明天补）

* markdown翻译了

* avl_tree.cpp翻译了

* 堆的cpp翻译

* modify the code format

* Update heap.md

---------

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

codes/cpp/chapter_heap/heap.cpp

@@ -63,4 +63,4 @@ int main()
     cout << "输入列表并建立小顶堆后" << endl;
     PrintUtil::printHeap(minHeap);
     return 0;
-}
+}