✨ [Feature]: grid 组件 树形表格添加树节点连接线功能

[David-TechNomad]

What problem does this feature solve

grid 组件 树形表格添加树节点连接线功能，层级多了增加连接线可以使层级显示更加明显 功能参考 #https://vxetable.cn/#/table/tree/line

What does the proposed API look like

:tree-config="{line: true}"

What is your project name

bom树表组件

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Title: ✨ [Feature]: grid component adds tree node connection line function to tree table