message: gltfpack: Fix JPEG frame parsing
  The last refactoring introduced an off-by-one error, making most JPEG
  files fail to parse.
diff: @@ -251,7 +251,7 @@ static bool getDimensionsJpeg(const std::string& data, int& width, int& height)
  if (data[offset] != '\xff')
  return false;
  - char marker = data[offset];
  + char marker = data[offset + 1];
  if (marker == '\xff')
  {
  