Dragging doesn't work with tr tags

[fukata]

Thank you for your wonderful library!

In another issue, I found that tr tags can also be dragged.

#23

However, I actually changed the demo and added a sample that drags the tr tag, but I couldn't drag it.

Do you have any problems with this?

The repository and branch to be reproduced are as follows.

https://github.com/fukata/vue-draggable-next/tree/reproduce-can-not-drag-table-tr

The fix commit is below.

fukata@c179f3e

that's all, thank you very much.