PHP 8.3 #[\Override] (#6273)

* PHP 8.3 #[\Override]
https://php.watch/versions/8.3/override-attr

With PHPStan `checkMissingOverrideMethodAttribute` https://phpstan.org/config-reference#checkmissingoverridemethodattribute

And modified the call to phpstan-next on the model of https://github.com/FreshRSS/Extensions/pull/228 (more robust than the find method, which gave some strange errors)

* Update extension example accordingly

app/Controllers/javascriptController.php

@@ -12,6 +12,7 @@ class FreshRSS_javascript_Controller extends FreshRSS_ActionController {
 		parent::__construct(FreshRSS_ViewJavascript::class);
 	}
 
+	#[\Override]
 	public function firstAction(): void {
 		$this->view->_layout(null);
 	}