A former employee of NFT marketplace OpenSea was found guilty Wednesday of what federal prosecutors described as the first insider-trading case involving digital tokens, marking a win for the Justice Department in its push to police the crypto industry. A federal jury in New York convicted Nathaniel Chastain of wire fraud and money laundering for using nonpublic information from his employer to trade on nonfungible tokens in 2021. The Manhattan U.S. attorney’s office charged Mr. Chastain in 2022, accusing him of purchasing the NFTs ahead of OpenSea featuring them on its home page.