Add md to md copy

src/main.rs

@@ -60,7 +60,7 @@ async fn process_file(
 }
 
 fn copy_readme(file: &DirEntry, readme_dir: PathBuf) {
-    let file_name = get_file_name(&file);
+    let file_name = get_file_name(&file) + ".md";
     let readme_path = get_output_path(readme_dir, &file_name);
 
     let _ = std::fs::copy(file.path(), readme_path);