Write AVIF image generation script

CHDataManagement/Generator/ImageGenerator.swift

@@ -38,8 +38,20 @@ final class ImageGenerator {
 
     private var avifCommands: Set<String> = []
 
-    func printAvifCommands() {
-        avifCommands.sorted().forEach { print($0) }
+    /**
+     Write a file to the output folder containing a script to generate all missing AVIF images.
+
+     - Note: AVIF images could be generated internally, but the process is very slow.
+     */
+    func writeAvifCommandScript() {
+        guard !avifCommands.isEmpty else {
+            if storage.hasFileInOutputFolder("generate-images.sh") {
+                storage.deleteInOutputFolder("generate-images.sh")
+            }
+            return
+        }
+        let content = avifCommands.sorted().joined(separator: "\n")
+        storage.write(content, to: "generate-images.sh")
     }
 
     /**