* forum: show image in full screen on click

* do not expand the whole site cause of big posted forum images, instead
show a small image and allow full size on click

system/pages/forum/new_post.php

@@ -116,4 +116,4 @@ if(Forum::canPost($account_logged))
 else
 	echo "Your account is banned, deleted or you don't have any player with level " . $config['forum_level_required'] . " on your account. You can't post.";
 
-?>
+echo $twig->render('forum.fullscreen.html.twig');