By Daniel Kline The fast-food leader hasn’t slowed down for the holidays like its key rivals McDonald’s, Wendy’s, and Burger King. The Christmas season is a busy time for fast-food chains. People are out shopping and they’re looking for a quick, comforting meal so they can get back to gift buying. Most of the major fast-food chains limit their menu innovation during this period to focus on serving hoards of hungry people. McDonald’s (MCD) – Get Free Report, for example, has its SZN of Savings promotion which focuses on offering deals rather than adding new menu items. Restaurant Brands Interna…