chore: Add LoadEditor event to psalm stubs

Signed-off-by: Julius Härtl <jus@bitgrid.net>

tests/stub.phpstub

@@ -673,4 +673,8 @@ namespace OCA\NotifyPush\Queue {
 		 */
 		public function push(string $channel, $message);
 	}
-}
+}
+
+namespace OCA\Text\Event {
+	class LoadEditor extends \OCP\EventDispatcher\Event {}
+}