Riverdale has found its mayor. Robin Givens has been cast in the recurring role of Mayor Sierra McCoy in the CW’s Greg Berlanti-produced Riverdale from WBTV. Set in present day and based on the iconic Archie Comics characters, Riverdale is a surprising and subversive take on Archie, Betty, Veronica, and their friends, exploring the surrealism of small town life — the darkness and weirdness bubbling beneath Riverdale's wholesome façade. McCoy is not only the powerful and…