Added hook_help into .module file.

Closes #3495149

alt_text_validation.module

@@ -5,36 +5,28 @@
  * Contains alt_text_validation.module.
  */
 
-/*
-use Drupal\Core\Entity\EntityInterface;
-use Drupal\Core\Entity\FieldableEntityInterface;
-use Drupal\Core\Form\FormStateInterface;
-use Drupal\file\Plugin\Field\FieldType\FileFieldItemList;
-*/
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\markdown\Markdown;
 
 /**
- * Implements hook_form_FORM_ID_alter().
- *
- * Alter the image_style_warmer form to insert a third option.
- *
- * Should be removed as part of va.gov-cms#4425 .
+ * Implements hook_help().
  */
-/*function va_gov_media_form_image_style_warmer_settings_form_alter(array &$form, FormStateInterface $form_state) {
-  $image_styles_config = \Drupal::configFactory()->get('image_style_warmer.settings');
-  $image_styles = $image_styles_config->get('vagov_image_styles');
-  $form['initial_image_styles']['#access'] = FALSE;
-  $form['queue_image_styles']['#access'] = FALSE;
-  $form['vagov_image_styles'] = [
-    '#type' => 'checkboxes',
-    '#title' => t('Late-generated image styles'),
-    '#description' => t('Select image styles which will be created after cropping.'),
-    '#options' => image_style_options(FALSE),
-    '#default_value' => !empty($image_styles) ? $image_styles : [],
-    '#size' => 10,
-  ];
-}*/
-
-
+function alt_text_validation_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    case 'help.page.alt_text_validation':
+      if (\Drupal::moduleHandler()->moduleExists('markdown')) {
+        // Use the Markdown filter to render the README.
+        // @phpstan-ignore-next-line
+        return Markdown::create()->loadFile(__DIR__ . '/README.md');
+      }
+      else {
+        $text = file_get_contents(__DIR__ . '/README.md');
+        return '<pre>' . Html::escape($text) . '</pre>';
+      }
+  }
+  return NULL;
+}
 
 /**
  * Implements hook_clientside_validation_validator_info_alter().