Support Deflate decoding (#1250)

tests/client.rs

@@ -24,6 +24,12 @@ async fn auto_headers() {
                 .unwrap()
                 .contains("br"));
         }
+        if cfg!(feature = "deflate") {
+            assert!(req.headers()["accept-encoding"]
+                .to_str()
+                .unwrap()
+                .contains("deflate"));
+        }
 
         http::Response::default()
     });