[iOS] Wrong UTI being used for allFiles

[scousino]

Currently the picker uses the public.content UTI for the allFiles types for iOS. However, this isn't accurate, in fact hardly any typical file conforms to public.content. The correct root for all files is public.item. This needs to be changed or referenced in the README.

I've added a link to the table of System-Declared UTI's that show how most files actually inherit from public.item, not public.content: https://developer.apple.com/library/archive/documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html#//apple_ref/doc/uid/TP40009259

[vonovak]

fixed in 4.1.1