use blurhash for nsfw images

since all images are covered with the same "careful here" placeholder, its literally impossible to tell if its gonna be porn, gore, or a cat

using blurhash would give a small idea, and it can be used as pre-pre-loader (before thumbnails), since its only a 28 char string, like LWLDMG9#0.xtKSs.$}WCPEs+xVt6 (smaller than filename), so can be simply included into post's json object