Add rule about not allowing AI images for your app's screenshots/images

There currently is no rule against adding AI images to the description or header of an app on the app store.
But apps like this https://apps.nextcloud.com/apps/journeys are very confusing because this is just a backend app yet shows some kind of AI generated image of something which doesn't exist.

If an app has a UI, then you should show an image that shows the UI.
But if you app doesn't and is only a backend thing... well then it won't have a header image and that's fine.

But having these AI images appear on the app store makes your app store appear less professional and frankly makes the apps on them appear like AI slop

https://apps.nextcloud.com/apps/journeys