NEW YORK — Vibe magazine has agreed to become the founding sponsor of the Urbanworld Film Festival, a competitive fest designed to showcase black cinema.The Urbanworld Film Festival will be held in conjunction with Vibe’s third annual music seminar from Aug. 20-23 in Gotham. Premiere magazine will also sponsor the event. The fest will accept works by black filmmakers as well as films about black culture by helmers of other races. “We are creating an all-access marketplace for these extraordinary films that otherwise would go unnoticed,” said Stacy Spikes, vice president of marketing for October Films. Spikes founded the Urbanworld fest along with producer Ariel Perets, former Miramax Films senior veepee Helena Echegoyen and others.