feat: Support for using React Ref to specify handle and cancel

[zhmushan]

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close #679

When I was writing this PR, I noticed that you used a very genius way to avoid possible problems caused by duplication of className.

However, the atomic class represented by Tailwind is becoming more and more popular, and many people no longer want to use className to do functional things, so I continue to complete this PR.

Also, this is my first time using this library and my first time using Flow, so please correct me if I'm doing something wrong.

Thanks again for your work, I have tried a lot of drag and drop libraries, react-draggable is the most suitable for my current product needs, thank you for saving me a lot of time.