add documentation for global batch actions

docs/crud/configuration.md

@@ -307,3 +307,33 @@ $configuration->setBatchAction(
     }
 );
 ```
+
+## setGlobalBatchAction
+
+`setGlobalBatchAction(string $context, string $action, string $label, callable $callack)`
+
+Add a global batch action. The callback has 3 arguments:
+
+* An instance of `App\Core\Repository\RepositoryQuery`
+* An instance of `App\Core\Manager\EntityManager`
+* An array of selected entities or a `null` value
+
+Do not use the same action in global and classic batch action.
+
+The callback can return a response. If not, the user will be redirect automatically. See the example below:
+
+```php-inline
+use App\Core\Entity\EntityInterface;
+use App\Core\Manager\EntityManager;
+
+$configuration->setGlobalBatchAction(
+    'index',
+    'export_json',
+    'Export to JSON',
+    function(RepositoryQuery $query, EntityManager $manager, ?array $selection): ?Response {
+        $items = $selection ?? $query->find();
+
+        return $this->json($items);
+    }
+);
+```