amend readme

Author: imoyao

sorts/readme.md

@@ -7,9 +7,12 @@
 - [插入排序](./insertion_sort)
 - [希尔排序](./shell_sort)
 <details>
-<summary><mark><font color=darkred>- 高级排序算法</font></mark></summary>
+<summary><mark><font color=darkred>高级排序算法</font></mark></summary>
+
     - [快速排序](./quick_sort)
+    
     - [归并排序](./merge_sort)
+    
 </details>