The first exchange-traded fund giving U.S. investors exposure to XRP had a roaring debut Thursday, bringing in close to $38 million in inflows in the best ETF launch of this year.  Rex Shares and Osprey Funds' XRP ETF surpassed expectations as investors rushed to get exposure to the cryptocurrency.  The issuers' DOJE ETF, the first Dogecoin ETF to trade in U.S. markets, generated a strong$17 million in its inaugural day.  The two funds' success indicated pent-up demand for altcoin exposure, Bloomberg Senio ...