Add first draft of cms page

docs/helpers/cms.md

@@ -0,0 +1,17 @@
+# CMS Helpers
+
+This helper provides utility methods to work with cms pages and layouts.
+
+## getDefaultCategoryLayout
+
+The `getDefaultCategoryLayout` method returns the cms page entity, which is created by shopware and represents the default category layout or null if it doesn't exists.
+
+```php
+<?php
+
+class MyFixture extends Fixture {
+    public function load(): void {
+        $cmsPage = $this->helper->Cms()->getDefaultCategoryLayout(); // [!code focus]
+    }
+}
+```