Allow lack of documentation on self-explanatory ExtendedColorType

src/color.rs

@@ -78,6 +78,7 @@ impl ColorType {
 ///
 /// Another purpose is to advise users of a rough estimate of the accuracy and effort of the
 /// decoding from and encoding to such an image format.
+#[allow(missing_docs)]
 #[derive(Copy, PartialEq, Eq, Debug, Clone, Hash)]
 pub enum ExtendedColorType {
     L1,