By Dan Weil On Wednesday, Ark snapped up shares of Twilio, Roblox, Coinbase and JD.com. It sold Twitter and Palantir Technologies. Investment star Cathie Wood, chief executive of Ark Investment Management, in recent weeks has made clear that she sees the declines in prices of young technology stocks as buying opportunities. And she’s acting on that call. On Wednesday, Ark snapped up shares of Twilio (TWLO) – Get Twilio, Inc. Class A Report, which provides software to developers; Roblox (RBLX) – Get Roblox Corp. Class A Report, an online videogame platform; Coinbase (COIN) , the largest U.S. cr…