To add the mouse wheel event processing for WindowBase

[llxwj]

Example:

textEdit.MouseWheel().Attach(func (x, y int, button walk.MouseButton) {
    delta := walk.MouseWheelEventDelta(button)
    keyState := walk.MouseWheelEventKeyState(button)
    fmt.Printf("x = %d, y = %d, delta = %d, keyState = %d\n",x, y, delta, keyState)
     //todo other
})

[lxn]

Thanks!