Stop event propagation when starting drag in order to support nested drag elements

[mrwatts]

Stop propagation of this event. In case we have nested drag components, we only want to drag the innermost dragged component, not start multiple drags at once (which isn't possible anyway)

[dathoangnd]

Hello, I have the same issue. Can someone review and consider merge mrwatts's request?

[mrwatts]

@dathoangnd what we did is we copied the files in this repo (there are only a few) into our project locally instead of using the package. It's very easy to do and at least you can carry on with your project.