Second Instance of Readarr on the User Control Panel

There was another request for this rejected a couple months ago. However, with the release on Audiobookshelf and Kavita + Calibre in development, I feel there would be more interest for users to have a second instance of Readarr available on the User Control Panel for their audiobook and manga/comic needs.

This would also make updating multiple instances much easier rather than having to use SSH and command line to do so.