Twitch, the eSports streaming platform that commands 15 million active users a day, has started live-streaming the National Basketball Association’s G League games, in a first-of-its-kind partnership between one of the major sports leagues and an over-the-top streaming service.Twitch began streaming the NBA G League, the NBA’s developmental league, on Dec. 15. The platform plans a heavy schedule of live games — up to six each week during the 2017-2018 season — and will also make past games available …