Ability to put pid value from defined attribute like data-cpid
currently photoswipe calculates pid as a image index in gallery, but what if we link photo on some external portal and we delete this photo from our gallery?... linked url will point to different photo that has the same pid = index of image in gallery
making it possible to set custom pid as a attribute data-cpid and let it be used to parse pid before open image
works great, THX!