fix gif caching

Pocket Poster/Packages/GIFImage/Sources/domain/CGImageSourceIterator.swift

@@ -0,0 +1,36 @@
+//
+//  File.swift
+//  
+//
+//  Created by Igor Ferreira on 05/04/2022.
+//
+
+import Foundation
+import ImageIO
+
+public actor CGImageSourceIterator: AsyncIteratorProtocol {
+
+    public let frameCount: Int
+    public let source: CGImageSource
+    public private(set) var currentFrame: Int
+
+    public init(source: CGImageSource) {
+        self.source = source
+        self.frameCount = CGImageSourceGetCount(source)
+        self.currentFrame = 0
+    }
+
+    public func next() async throws -> ImageFrame? {
+        guard currentFrame < frameCount else {
+            return nil
+        }
+
+        let frame: ImageFrame? = if let image = CGImageSourceCreateImageAtIndex(source, currentFrame, nil) {
+            ImageFrame(image: image, interval: source.intervalAtIndex(currentFrame))
+        } else {
+            nil
+        }
+        currentFrame += 1
+        return frame
+    }
+}