[Feature Request] Tree Virtual Scroller

### Existing Component
Yes

### Component Name
Tree

### Description
Hey, I have a project I'm working on where I need to implement a tree (I'm currently trying to use the Element UI Tree) that has a huge amount of nodes. Despite the use of the lazy load feature, the tree is still not performing well. I searched the docs and can't find a way to force the tree to use a virtual scroller, is there a way to do this? Or maybe a way to use vue-virtual-scroller with Element UI Tree?

Thanks in advance :D