message: Add derives for `Hash`, `PartialEq` and `Eq`.
diff: @@ -449,7 +449,7 @@ where
  ///
  /// image::imageops::overlay(&mut img, &on_top, 128, 128);
  /// ```
  -#[derive(Debug)]
  +#[derive(Debug, Hash, PartialEq, Eq)]
  pub struct ImageBuffer<P: Pixel, Container> {
  width: u32,
  height: u32,
  