onevcat/Kingfisher ? reverse-engineered prompt

Build me a lightweight Swift library for downloading and caching images from the web, kind of like a simple drop in image loading tool for iOS, macOS, tvOS, watchOS, and SwiftUI apps.

I want it to fetch remote images asynchronously, cache them in memory and on disk, and show them right away when the same URL is used again. It should support placeholders, loading indicators, fade in transitions, canceling in flight requests, prefetching, and a few useful image processing options like resizing, downsampling, and rounded corners. Please make it easy to use with UIImageView, NSImageView, UIButton, and SwiftUI views, so I can do something like set an image from a URL with very little code.

Keep it clean, fast, and modular, with good docs and a small demo app showing the main features. If you need to check current Swift and Apple platform guidance, look it up online first.