🧐[DragSortTable] 在嵌套表格下如何使用

https://github.com/ryanhanwu/How-To-Ask-Questions-The-Smart-Way/blob/main/README-zh_CN.md

### 🧐 问题描述
DragSortTable 在data格式是嵌套数据时 一级以下的数据不能进行拖拽
想问一下 有没有办法支持

### 复现仓库
https://github.com/sdmu-gaoqi/proComponent-table

Start with the DragSortTable implementation and the reproduction repository linked in the issue, using the nested data case described there. Confirm how dragging behaves below the first level and compare it with a flat table. Done means nested rows at levels below the first can also be dragged, with the expected behavior verified in the reproduction case.

Written by the indexing model from the issue text.