Feature Request: Expose UserDirs for users other than the current user

[TechnoPorg]

On a system with multiple users - for instance, Foo and Bar - it would be nice to be able to enumerate all UserDirs on the system, with one struct returned per user, each of which will have the paths for that user, like /home/Bar/Downloads and /home/Foo/Downloads.

Thanks for your hard work on this crate!