set doc attribute on Exchange variants

src/crypto.rs

@@ -703,7 +703,10 @@ macro_rules! make_exchange {
         #[allow(non_camel_case_types)]
         #[repr(u8)]
         pub enum Exchange {
-            $($ticker = $code),*
+            $(
+                #[doc = $name]
+                $ticker = $code
+            ),*
         }
 
         impl Exchange {