Export createDataTransfer util function

[DanielGibbsNZ]

Problem description

When testing paste functionality, it would be really helpful to be able to use the internal createDataTransfer functionality.

I've previously created a simple mock of the DataTransfer object but this can cause frustrating test failures when it doesn't behave in exactly the same way that user-event expects it to, e.g. returning the text/plain data when getData('text') is called.

Suggested solution

Since user-event's paste functionality seems to expect that the mocked DataTransfer object behaves as the internally mocked version does, it would be really helpful to expose createDataTransfer to allow the user to create an instance of that version.

Additional context

No response