improve type def for buttonIcons/bootstrapFontAwesome option. fixes #5548
improve type def for buttonIcons/bootstrapFontAwesome option. fixes #5548

arshaw/fullcalendar,arshaw/fullcalendar,oleg-babintsev/fullcalendar,arshaw/fullcalendar,arshaw/fullcalendar,fullcalendar/fullcalendar,fullcalendar/fullcalendar,oleg-babintsev/fullcalendar,fullcalendar/fullcalendar,oleg-babintsev/fullcalendar,fullcalendar/fullcalendar