added doc comments

Hi, Opened this new MR.

library_generator.module

 <?php
 
+/**
+ * @file
+ * library_generator module file.
+ */
+
+/**
+ * Implements hook_library_info_alter().
+ */
 function library_generator_library_info_alter(&$libraries, $extension) {
   $generated_libraries = \Drupal::service('library_generator.discovery')->getLibrariesByExtension($extension);
   $libraries = array_merge($generated_libraries, $libraries);
-}
+}
\ No newline at end of file