Commie and join us! Mayor Zohran Mamdani’s election has emboldened members of a new offshoot of the Communist Party in the Big Apple — as its members push Hizzoner to bolt the Democratic Party to jumpstart a radical alternative. The Revolutionary Communists of America held more than a dozen events in and around New York City the past month, but its leaders told The Post the fledgling mayor needs to focus on overthrowing capitalism by launching a new workers party. “Building a mass workers’