Issue #3271920 by RenatoG: After the validation on special char explain that...

Issue #3271920 by RenatoG: After the validation on special char explain that is possible to modify that in the settings page

src/Service/BlockClassHelperService.php

@@ -737,8 +737,12 @@ class BlockClassHelperService {
         // Verify if there is a special char on this class.
         if (preg_match('/[\'^£$%&*()}{@#~?><>,|=+¬]/', $item)) {
 
+          $url_settings_page = Url::fromRoute('block_class.settings')->toString();
+
           // If there is a special chat return the error for the user.
-          $form_state->setErrorByName('class][third_party_settings][block_class][' . $key, $this->t("In class is allowed only letters, numbers, hyphen and underline"));
+          $form_state->setErrorByName('class][third_party_settings][block_class][' . $key, $this->t('Special chars is not enabled in the class value. To enable this, go to the <a href="@url_settings_page@">settings page</a>', [
+            '@url_settings_page@' => $url_settings_page,
+          ]));
 
         }