让 Kingfisher 支持 webp 图片

1. 引入 KingfisherWebP 库

   pod 'KingfisherWebP'

2. 添加 options

   [.processor(WebPProcessor.default), .cacheSerializer(WebPSerializer.default)]

   self.kf.setImage(with: URL(string: string),
                    placeholder: placeholder,
                    options: [.processor(WebPProcessor.default), .cacheSerializer(WebPSerializer.default)]) { (img, err, cacheType, imgUrl) in
   
   }