feat(TreeView):希望给树形组件添加连接线

[Idle-wang]

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Describe the solution you'd like

希望给树形组件添加连接线，这样看起来结构会更清晰，如下图所示

Additional context

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[bb-auto[bot]]

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[ArgoZhang]

@Idle-wang 如果用户使用样式更改了行高或者字体大小，这些连接线如何处理？