请教下：做缩放动画时，画面会有抖动的感觉，不流畅，如何解决呢？ #26
Description
demo.mp4
demo代码如下：
func scaleAnimationDemo() -> VideoLab {
// 1. LayerGroup
var timeRange = CMTimeRange(start: CMTime.zero, duration: CMTime(seconds: 5, preferredTimescale: 600))
let keyTimes = [CMTime(seconds: 0, preferredTimescale: 600),
CMTime(seconds: 5, preferredTimescale: 600)]
let animation1 = KeyframeAnimation(keyPath: "scale",
values: [1, 1.2],
keyTimes: keyTimes,
timingFunctions: [.quadraticEaseInOut])
var transform = Transform.identity
transform.animations = [animation1]
// Add sub-renderLayer1
let image = UIImage(named: "image2.HEIC")
let imageSource = ImageSource(cgImage: image?.cgImage)
imageSource.selectedTimeRange = CMTimeRange(start: CMTime.zero, duration: timeRange.duration)
timeRange = imageSource.selectedTimeRange
let renderLayer1 = RenderLayer(timeRange: timeRange, source: imageSource)
renderLayer1.transform = transform
// 2. Composition
let composition = RenderComposition()
composition.renderSize = CGSize(width: 2016, height: 1512)
composition.layers = [renderLayer1]
// 3. VideoLab
let videoLab = VideoLab(renderComposition: composition)
return videoLab
}