Helper for page / controller specific styling, adding the class and parent classes of your
pages to your body element. E.g. a CustomCalendarPage that extends CalendarPage
would produce CustomCalendarPage CalendarPage.
That way any specific styles for CalendarPage will also apply for CustomCalendarPage.
Install via composer and add $BodyCssClasses to your body or, wherever you want it.
E.g.:
<body class="$BodyCssClasses">
</body>