The bride and groom left the chuppah, smiling widely, and proceeded up the aisle. “We paused,” said Rebecca Rose. “And we took out our phones.” She and her now-husband, Peter Kacherginsky, weren’t texting, and they weren’t making a sudden pivot to Instagram. Instead, the newlyweds were using their phones for an entirely modern ritual, sending each other copies of a piece of animated art that contained a nonfungible token, or NFT, a unique and permanent digital marker. Both of them work in blockchain, the technology that underpins NFTs, and it was a way for the San Francisco couple...