ProShares, the Bethesda, Maryland-based premier provider of alternative ETFs and the world’s largest provider of geared (leveraged and inverse) exchange traded funds, has announced the launch of a merger-arbitrage ETF this week. The ProShares Merger ETF (MRGR), the firm’s 13th launch this year, is listed on the BATS exchange and would compete with IndexIQ’s ARB Merger Arbitrage ETF (MNA). MRGR …