The new `will-resize` event can be used to prevent the resize from
happening before the native window is actually resized. This is in
contrast to the existing the `resize` event, which is sent *after* the
native window has already been resized. For apps with e.g. custom window
snapping logic, the `resize` event is not sufficient because it will
result in flickering between the dragged size and the snapped size.
`will-resize` is only emitted on macOS and Windows.
