The sidewalk vendors of Times Square sell cheap metal signs bearing the image of Spider-Man, no doubt unaware that the superhero’s co-creator walks right past them every day, completely unrecognized. Then again, only a handful of people in the world would recognize Steve Ditko, the mysterious 84-year-old artist who, with writer Stan Lee, dreamed up the wall crawler back in 1962. ...When The Post knocked on his door, Ditko — who turns out to be a owlish man with wisps of white hair and ink-stained hands, wearing large black glasses and an unbuttoned white shirt with a white tee beneath...