Default italic rendering of "onVisible" labels

++ What: in ''handle()'' embrace "htmlspecialchars($return['onVisible'])" with DokuWiki Italic marks "//"
++ Why: Easy distinguishability between visible (title in Italics) and hidden (title "normal") parts
++ Note: Very useful with many consecutive hidden sections of which always only one will be clicked to be visible; in a more matured version Italics might be a configuration choice