New MacOS .icon file support - MacOS 26 Liquid Glass icons

Apple has introduced a new icon format (.icon) in MacOS 26. It's for their fancy Liquid Glass style. They have layers, dynamic lighting effects, react to light/dark mode, allow tinting, and probably much more. Not something we could ever emulate with a PNG.

Luckily it produces a nice .icon file (actually a MacOS package).

Feature Request

• Add support for .icon packages to the -i / --icon option (and similar spec config)
• Test the app icon still works on older version of MacOS. Xcode will create a flattened one automatically, but not sure if we'll get that for free using Xcode CLI build tools.

References

• Icon composer app from Apple to create these icons: https://developer.apple.com/icon-composer/
• Appel design docs: https://developer.apple.com/design/human-interface-guidelines/app-icons
• Attaching an example icon mac_icon_example.zip