* fix missing errors doc warnings * cargo +nightly fmt * Update frame/nfts/src/features/create_delete_item.rs * Update frame/nfts/src/features/create_delete_item.rs * Update frame/nfts/src/features/transfer.rs * Update frame/nfts/src/features/create_delete_collection.rs * add intra doc linking for errors * fmt * Apply suggestions from code review Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io> --------- Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>