Hello,

While testing this library in Cypress with a third party vendor integration, I have noticed that when invoking realMouseMove after realMouseDown the move emitted event to Cypress.automation doesn't provide a button property which indicates the testing browser that the mouse move is happening while a button is pressed.

On your tests, specifically on canvas-drag.html, you have created a mousedown event handler that sets a state variable to true (mouseDown = true) when Cypress (and the tests) triggers the `realMouseDown``

In our use case, it's a third party vendor who handles the mouse events, so we are not able to control how they handle these.

I have implemented a patch in my local, that I have verified it's now working in my project's Cypress tests.
I am going to open a PR to implement this new feature in order to resolve this issue.

Thanks,
Jesús