Drag'n'drop with text/plain is currently prevented, and cannot be overriden

[broehl-ptc]

Does this try-catch block, with setting the "text/plain" type still makes sense? If yes, can this be done before calling the user's callback handler?

https://github.com/react-component/tree/blob/a45cf7bc879a5b928a2e21313553f6cc8739aa7d/src/TreeNode.tsx#L127