Tree Component

[zhaopuming]

Hi Jason，

I'm using this library to create a simple demo ui, and found that there is no tree component right now.

I checked the source code of Zed, and found their ProjectPanel is a tree view, but is deeply coupled with project management.

Are you interested in developing a Tree component for more general uses?

In my scenario, a tree component should:

1. Put in a sidebar
2. Be able to expand and collapse
3. on click of an entry, could switch to a different view in the main dock-area

[huacnlee]

This may not plan to do in recent months. I have written this library to used in our product. But we not need Tree, so it not a first priority.

[zhaopuming]

OK. I'll check the tree in Zed's ProjectPanel class and simplify it into a generalized widget.