Add iCloud Container backend

[landoncolburn]

Since the policy shift on the App Store, would it now be possible to have a iCloud App Container backup option? I will admit I'm not familiar with the Harmony codebase (I'm coming here off the Delta repo), but I would be willing to put in some work if needed to bring this feature. Just want to make sure there is not technical or otherwise limitations that I might not be privy to.

[ebelair]

Up ⬆️ Willing to help too!