Fix to correctly handle date-times when timezone Id is provided

[chamakura]

It looks like the parsing logic to extract date-times isn't handling timezones correctly. The way it's correctly implemented, it's assumed that the provided timestamp value is in UTC even when a corresponding timezone value is provided. This change factors in the timezone (when available) to correctly convert the value in UTC. (This is to handle #3 in https://www.kanzaki.com/docs/ical/dateTime.html)

This issue manifested in MagicMirror where events scheduled by someone in a different timezone were getting offset. For example, if someone in New York (timezone=America/New_York) sent me (I'm in timezone=America/Los_Angeles) an invite, the event would show up 3 hours later than expected because that's the difference between the timezones.

[peterbraden]

This adds a library to ical.js. Because it's intended that ical.js can be used in a browser without a build step, this won't work - would it be possible to extract the necessary logic from moment-tz?

[chamakura]

I see - let me look into adding this without the library dependency.

[chamakura]

So it looks like one option is to inline the dataset corresponding to all available timezones: https://github.com/moment/moment-timezone/blob/develop/builds/moment-timezone-with-data-10-year-range.js#L693
Would this be OK?

Or is there a way to dynamically link to dynamically link to https://momentjs.com/downloads/moment-timezone-with-data-10-year-range.min.js?