a Hebcal holiday event (not a parsha hashavua event)
Optionalil: boolean = false
true for the Israel schedule (default false)
Optionallanguage: string = 'en'
language for names and summary (default 'en')
the holiday leyning, or undefined if this event has no reading
Looks up the leyning for a holiday event.
Depending on the holiday, the result may include the full kriyah, a special maftir, one or more Haftarot, and/or a megillah.