Add explainer docblock that pageview is not official event

Author: Alex Westergaard

src/Event/PageView.php

@@ -5,6 +5,12 @@
 use AlexWestergaard\PhpGa4\Helper\EventHelper;
 use AlexWestergaard\PhpGa4\Facade;
 
+/**
+ * This is not an official SST Event, please use this with caution
+ * 
+ * @link https://developers.google.com/analytics/devguides/collection/ga4/views?client_type=gtag
+ * @internal
+ */
 class PageView extends EventHelper implements Facade\Type\DefaultEventParamsType
 {
     protected null|string $method;