Update README.md

Author: zzzhangboya

README.md

@@ -26,7 +26,7 @@
 ### 数据结构篇 🐰
 
 - [二叉树](./data_structure/binary_tree.md)
-- [链表](./data_structure/linked_list.md)
+- [链表√](./data_structure/linked_list.md)
 - [栈和队列](./data_structure/stack_queue.md)
 - [优先级队列 (堆)](./data_structure/heap.md)
 - [并查集](./data_structure/union_find.md)