fix(phpstan): correct variable type

Related: #4 (closed)

src/QUI/Interview/Controls/IntervieweeData.php

@@ -35,7 +35,7 @@ public function __construct($attributes = [])
 
         parent::__construct($attributes);
 
-        $this->setAttribute('cacheable', 0);
+        $this->setAttribute('cacheable', "0");
     }
 
     /**
@@ -43,7 +43,7 @@ public function __construct($attributes = [])
      *
      * @see \QUI\Control::create()
      */
-    public function getBody()
+    public function getBody(): string
     {
         $Engine = QUI::getTemplateManager()->getEngine();
         $Site   = $this->getSite();