Caller of FileManager's unzipItem(at:to:skipCRC32:progress:preferredEncoding:) need to know what was unzipped

[valeriyvan]

Is your feature request related to a problem? Please describe.
In most use cases of FileManager's unzipItem(at:to:skipCRC32:progress:preferredEncoding:) callers need to know what was unzipped. Now this can be achieved by reading contents of destination. That's extra file operation.

Describe the solution you'd like
This method should return an array of URL's of unzipped items.

Describe alternatives you've considered
Alternatively method might have optional delegate or callback parameter.

Additional context
n/a

[weichsel]

I think the best way to handle this would be to provide a delegate with a similar API as the FileManager delegate.
E.g. something like fileManager(FileManager, didUnzipEntry: Entry, to: URL).

This would also solve: #54