Issue #3333729: hook_help function missing in .module file

swiffy_slider.module

 <?php
+/**
+ * @file
+ * Primary module hooks for Swiffy Slider module.
+ */
 
 declare(strict_types=1);
 use Drupal\Core\Template\Attribute;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Template\AttributeHelper;
 
 /**
- * @file
- * Primary module hooks for Swiffy Slider module.
+ * Implements hook_help().
  */
+function swiffy_slider_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    // Main module help for the swiffy_slider module.
+    case 'help.page.swiffy_slider':
+      $output = '';
+      $output .= '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('Swiffy Slider provides a lightweight slider/carousel solution. All the sliding, dragging, snapping etc. are native browser behavior and not Javascript.') . '</p>';
+      return $output;
 
-use Drupal\Core\Template\AttributeHelper;
+    default:
+  }
+}
 
 /**
  * Implements hook_theme().