MarketWatch photo illustration/iStockphoto Cryptocurrency markets might be cooling off, but the hype around blockchain isn’t abating, judging by the popularity of exchange-traded funds centered on the technology. Four new ETFs, all promising to give investors exposure to blockchain technology, launched in January. The latest is the Innovation Shares NextGen Protocol ETF, which trades under the ticker KOIN KOIN, -1.04% and made its debut on the New York Stock Exchange on Tuesday. The newcomer...