[FEAT]: Would like to have VALARM parsed

[mbeynon]

I'm using this through the node-red integration to help an elderly relative avoid missing doctor appointments that are 30+ min away. They have calendar events for these with a notification for when they need to leave.

My plan was to use the node-red nodes that wraps this library to trigger a Google Home text to speech reminder to leave for the appointment. It all works, but there's nothing in the parsed json for the event to represent the event start time and the notification time (e.g., 30 min before).

Seems like this could be done by having a new flag to ical-trigger node that means "include the earliest notification offset in the trigger countdown". I searched the git repo for "VALARM" and don't see it anywhere, so I suspect it's just skipped by the parser.

A sample of what this looks like for a single 1 minute before notification within a VEVENT block is:

BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:This is an event reminder
TRIGGER:-P0DT0H1M0S
END:VALARM