Apple has started using its iTun.es domain as a URL shortener, while adding playlist sharing to Ping, its new music-focused social network. The iTun.es domain, which Apple purchased in 2006, is now used for shortening URLs in Twitter updates sent from Ping. A 9 to 5 Mac notes, Apple previously used the t.co URL shortening service with Ping. In addition, Apple has added the ability for Ping users to create playlists which can be shared, added to by…