NEW YORK (Reuters) - McDonald’s Corp is hoping 2021 is the year it cracks the crispy chicken sandwich by rolling out three different versions in the United States, the company told Reuters. The world’s biggest burger chain will add the new sandwiches - including a spicy version - on Feb. 24 as it takes on major chicken chains such as Restaurant Brands International Inc’s Popeyes, in a play for a share of a growing market.