Add text mode to dom_str_replace migrate process plugin

Closes #3427939

src/Plugin/migrate/process/DomStrReplace.php

 <?php
 
-declare(strict_types = 1);
+declare(strict_types=1);
 
 namespace Drupal\migrate_plus\Plugin\migrate\process;
 
@@ -19,6 +19,7 @@ use Drupal\migrate\Row;
  * - mode: What to modify. Possible values:
  *   - attribute: One element attribute.
  *   - element: An element name.
+ *   - text: The element text content.
  * - xpath: XPath query expression that will produce the \DOMNodeList to walk.
  * - attribute_options: A map of options related to the attribute mode. Required
  *   when mode is attribute. The keys can be:
@@ -70,6 +71,12 @@ use Drupal\migrate\Row;
  *       search: '/foo-(\d+)/'
  *       replace: 'bar-$1'
  *     -
+ *       plugin: dom_str_replace
+ *       mode: text
+ *       xpath: '//a'
+ *       search: 'Find more information here'
+ *       replace: 'More information'
+ *     -
  *       plugin: dom
  *       method: export
  * @endcode
@@ -96,6 +103,7 @@ class DomStrReplace extends DomProcessBase {
           'attribute_options' => NULL,
         ],
         'element' => [],
+        'text' => [],
       ],
       'search' => NULL,
       'replace' => NULL,
@@ -218,6 +226,9 @@ class DomStrReplace extends DomProcessBase {
 
       case 'element':
         return $node->nodeName;
+
+      case 'text':
+        return $node->textContent;
     }
   }
 
@@ -231,6 +242,7 @@ class DomStrReplace extends DomProcessBase {
     switch ($this->configuration['mode']) {
       case 'attribute':
       case 'element':
+      case 'text':
         return $this->configuration['search'];
     }
   }
@@ -245,6 +257,7 @@ class DomStrReplace extends DomProcessBase {
     switch ($this->configuration['mode']) {
       case 'attribute':
       case 'element':
+      case 'text':
         return $this->configuration['replace'];
     }
   }
@@ -299,6 +312,10 @@ class DomStrReplace extends DomProcessBase {
         }
         $html_node->parentNode->replaceChild($new_node, $html_node);
         break;
+
+      case 'text':
+        $html_node->textContent = $new_subject;
+        break;
     }
   }