JSX in TreeItem.title

# Reporting a Bug?

Please include either a failing unit test or a simple reproduction. You can start by forking the [CodeSandbox example](https://codesandbox.io/s/wkxvy3z15w)

I wanted to display an icon for each node, such as this:

I did it this way:

But I had an issue where whenever I collapse/expand a node, it would re-render forever and the browser would be unresponsive forever.

I tried this, just to check:

And same thing. It seems to me that just having JSX in the title, causes react-sortable-tree to freeze the browser. It would be a good feature to have.

The thing is. It renders fine, it's just that when you collapse/expand, it freezes.