NEW ORLEANS — Zion Williamson celebrated a recent alley-oop dunk with an ebullient smile and a flexed left bicep as an energized crowd roared approvingly. The NBA preseason has provided a tantalizing taste of the excitement the league’s top overall draft choice – a charismatic, 6-foot-6, 285-pound force of nature – could bring to New Orleans’ long moribund small-market franchise. Energetic crowds well in excess of 10,000 showed up for the Pelicans’ first few exhibition contests, whether at home or on the road, rumbling with anticipation when Williamson had the ball and erupting when he launched his massive frame skyward to throw down rim-rattling dunks. “We would have loved to have crowds like this for any game last year,” Pelicans fifth-year coach Alvin Gentry said following his club’s lone home exhibition game. “In the years I’ve been here, I’ve never seen this much interest in the start of a basketball season.” The Pelicans look primed to play entertaining and compelling basketball, whether or not they emerge as playoff contenders this season. Williamson has shown no fear against established NBA big men, routinely scoring 20-plus points during exhibition games. The former Duke star also doesn’t seem fazed by the enormous expectations…