DAEGWALLYEONG, South Korea — Jamie Anderson is a highflying, trailblazing, free-spirited snowboarding daredevil who, by now, has grown plenty accustomed to being the best, the baddest — and the first. Anderson added to her medal haul by winning silver in the women’s big air competition Thursday morning in Pyeongchang, becoming the first female snowboarder to win two medals at a single Olympics.