feat: add stubbed quota response

Author: Sn0wCrack

src/Testing/FakeFolder.php

@@ -136,6 +136,25 @@ public function expunge(): array
         return [];
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function quota(): array
+    {
+        return [
+            'MESSAGES' => [
+                'usage' => 0,
+                'limit' => 0,
+            ],
+            'STORAGE' => [
+                'usage' => 0,
+                'limit' => 0,
+            ],
+            'usage' => 0,
+            'limit' => 0,
+        ];
+    }
+
     /**
      * {@inheritDoc}
      */