Web.HTML.Window.(scrollX|scrollY) should have type `Window -> Effect Number`

Turns out that [scrollY](https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollY) and [scrollX](https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollX) in `Web.HTML.Window` can return subpixel values!

I suppose the type needs to be changed from `Window -> Effect Int` to `Window -> Effect Number`.