Update `DesignableGradientView`
Update `DesignableGradientView`

alexiosdev/IBAnimatable,IBAnimatable/IBAnimatable,JakeLin/IBAnimatable,alexiosdev/IBAnimatable,IBAnimatable/IBAnimatable,seanwoodward/IBAnimatable,IBAnimatable/IBAnimatable,seanwoodward/IBAnimatable,JakeLin/IBAnimatable