If all you want for Christmas is MARIAH CAREY and McDonald's, you're in luck.  She's here to bring 12 days of FREE food with her, quote, "Mariah Menu".     There's only a few small catches . . . the promotion is ONLY available in the McDonald's app . . . and you have to spend at least $1 to be eligible for the free daily item.  It'll start on December 13th and run through the 24th. Some of the "free" items include a Big Mac, apple pie, 6-piece chicken McNuggets, and breakfast items like pancakes and a sausage egg McMuffin.  Each day [...]