feat: implement check_outdated

src/main.rs

@@ -61,5 +61,16 @@ fn get_dist_path(
 }
 
 fn check_outdated(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> bool {
-    true // TODO
+    let up_to_date = dst
+        .as_ref()
+        .metadata()
+        .and_then(|meta| meta.modified())
+        .is_ok_and(|dst_mtime| {
+            src.as_ref()
+                .metadata()
+                .and_then(|meta| meta.modified())
+                .is_ok_and(|src_mtime| src_mtime <= dst_mtime)
+        });
+    // either we cannot get metadata or src_mtime > dst_mtime (outdated)
+    !up_to_date
 }