message: Check color type properly
diff: @@ -68,8 +68,15 @@ impl<W: Write> ImageEncoder for QoiEncoder<W> {
  buf: &[u8],
  width: u32,
  height: u32,
  - _color_type: ColorType,
  + color_type: ColorType,
  ) -> ImageResult<()> {
  + if !matches!(color_type, ColorType::Rgba8 | ColorType::Rgb8) {
  + return Err(ImageError::Encoding(EncodingError::new(
  + ImageFormat::Qoi.into(),
  + format!("unsupported color type {color_type:?}. Supported are Rgba8 and Rgb8."),
  + )));
  + }
  +
  // Encode data in QOI
  let data = qoi::encode_to_vec(buf, width, height).map_err(encoding_error)?;
  