Wandering Trader sells Sherds and Music Discs

The Wandering Trader should very rarely sell Sherds and/or Music Discs.

Currently, it isn't really exciting when a Wandering Trader shows up. Hopefully, by adding Sherds and Music Discs players will be more excited when the Wandering Trader shows up.

Perhaps half of the Creeper-Skeleton Music Discs can be moved into the Wandering Traders pool.