Add derives (#42)

src/chunk.rs

@@ -10,6 +10,7 @@ use super::*;
 /// able to write two things at the same time (which isn't possible with a
 /// single chunk because of the streaming nature --- only one writer can borrow
 /// it at a time).
+#[derive(Clone)]
 pub struct Chunk {
     pub(crate) buf: Vec<u8>,
     pub(crate) offsets: Vec<(Ref, usize)>,

src/color.rs

@@ -1304,6 +1304,7 @@ impl OutputIntent<'_> {
 }
 
 /// The output intent subtype.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum OutputIntentSubtype<'a> {
     /// `GTS_PDFX`
     PDFX,