It’s-a-us, Marios! A horde of “socially awkward” gamers side-scrolled their way into Midtown this week to celebrate Nintendo’s “Mario Day” — and join together for what organizers say was the largest gathering ever of fans dressed as as the beloved Nintendo video game character. A whopping 270 participants flocked to the real-life Mario Party purely for the love of the game and for the decades of joy the Brooklyn plumber had brought them. “Mario’s from New York, so New York really showed up for