Add support for #[derive] annotations

examples/simple.rs

@@ -3,6 +3,7 @@ mod config {
     use std::path::PathBuf;
 
     confique::config! {
+        #[derive(Clone)]
         log: {
             /// Determines how many messages are logged. Log messages below
             /// this level are not emitted. Possible values: "trace", "debug",
@@ -12,8 +13,8 @@ mod config {
             /// If this is set, log messages are also written to this file.
             #[example = "/var/log/test.log"]
             file: Option<PathBuf>,
-        }
-    },
+        },
+    }
 }