From an event's date, type and title, derives the key used to look up its
reading in holiday-readings.json (accounting for Shabbat, Rosh Chodesh,
Chol ha-Moed, and the Israel vs. Diaspora schedule).
Parameters
ev: Event
the holiday event
Optionalil: boolean = false
true for the Israel schedule (default false)
Returns string|undefined
the reading key for holiday-readings.json, or undefined if the
event has no reading
From an event's date, type and title, derives the key used to look up its reading in
holiday-readings.json(accounting for Shabbat, Rosh Chodesh, Chol ha-Moed, and the Israel vs. Diaspora schedule).