Implement Debug for Decoder and Encoder

[LiosK]

Would it be possible to implement Debug for Decoder and Encoder? Even just opaque output like the snippet below would be really useful - it lets downstream types derive Debug without any extra effort:

impl core::fmt::Debug for Decoder {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.write_str("Decoder { .. }")
    }
}

impl core::fmt::Debug for Encoder {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.write_str("Encoder { .. }")
    }
}

Thanks!

[LiosK]

Alternatively, even just exposing the encoding name would go a long way:

impl core::fmt::Debug for Decoder {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_struct("Decoder")
            .field("encoding", self.encoding)
            .finish()
    }
}

impl core::fmt::Debug for Encoder {
    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
        f.debug_struct("Encoder")
            .field("encoding", self.encoding)
            .finish()
    }
}