The ItemEnclosure property returns a string which specifies
a URL that links to an attached document for the news feed item. This
is similar to an attachment in an email message, however instead of
the item containing the contents of the attached file, it only
specifies a link to the file. Enclosures are most commonly used with
podcasting where an item is linked to an audio or video file, however
the link may reference any type of file. If there is no enclosure
specified for the current item, this property will return an empty
string.