Is there a better alternative to Google Calendar for events?

@krassowski raised this question in #571

> Maybe we could consider using an alternative to Google Calendar which is fully privacy-respecting and responsive?

He adds:

> One option would be https://fullcalendar.io/ which supports fetching from public Google Calendar: https://fullcalendar.io/docs/google-calendar.

Start by reading the context in issue #571 and reviewing FullCalendar's public Google Calendar documentation at fullcalendar.io. Compare the privacy and responsiveness requirements against the current events setup, then document a decided alternative and the integration scope; the issue does not name a file or test to run.

Written by the indexing model from the issue text.