Mayor de Blasio has groundhog blood on his hands! A week after Hizzoner dropped Staten Island Chuck in front of a crowd of spectators on Feb. 2, the winter-weather prognosticator died of internal injuries — and then the coverup began, The Post has learned. Staten Island Zoo officials went to great lengths to hide the death from the public and keep secret the fact that “Chuck” was actually “Charlotte,” a female imposter, sources said Wednesday. The stand-in was found dead in her enclosure at the Staten Island Zoo on Feb. 9 — and a necropsy determined she died from “acute...