NEW YORK — U.S. President-elect Donald Trump celebrated his election victory on Saturday night by attending an Ultimate Fighting Championship event with billionaire friend Elon Musk and cheering fans at a heavily guarded Madison Square Garden in New York City. Known by some in the mixed martial arts world as the “Combatant in Chief,” Trump counts UFC President Dana White as a close friend and considers fans of the sport part of his political base. Trump sat between White and Musk and paid rapt attention to the fights. He entered the arena to loud music and waved to the crowd