message: Allow loading alpha-only TGAs as L8
diff: @@ -153,6 +153,7 @@ impl<R: Read + Seek> TgaDecoder<R> {
  (0, 24, true) => self.color_type = ColorType::Rgb8,
  (8, 8, false) => self.color_type = ColorType::La8,
  (0, 8, false) => self.color_type = ColorType::L8,
  + (8, 0, false) => self.color_type = ColorType::L8, // alpha-only image is treated as L8
  _ => {
  return Err(ImageError::Unsupported(
  UnsupportedError::from_format_and_kind(
  