message: Update image crate ImageFormat enum usage
diff: @@ -21,7 +21,7 @@ In order to load the image, we just need to use `image::load`:
  ```rust
  use std::io::Cursor;
  let image = image::load(Cursor::new(&include_bytes!("/path/to/image.png")[..]),
  - image::PNG).unwrap().to_rgba();
  + image::ImageFormat::Png).unwrap().to_rgba();
  let image_dimensions = image.dimensions();
  let image = glium::texture::RawImage2d::from_raw_rgba_reversed(&image.into_raw(), image_dimensions);
  ```
  