Fixes custom wallpapers not appearing in Settings
Since iOS 12, custom wallpapers stored in /Library/Wallpapers won't appear in Settings when choosing a new wallpaper.
This tweak allows you to store custom wallpapers in /Library/Wallpapers again and lets you use iOS' "special handling" (eg. centering and zoom) of system wallpapers for your own.
Custom wallpapers are always appended to the list after stock wallpapers.