Adding events to a calendar

[kipcole9]

In conversion with @dbernheisel the topic of adding events to a formatted calendar came up. It has been on the "to do" list for a while so this issue is to track design ideas.

My initial thoughts are:

Design goals

1. An :events option can be passed to Cldr.Calendar.Format.{week, month, year}/2
2. A module implementing the Cldr.Calendar.Formatter behaviour will would include a format_event/2 function which is passed an event and some options
3. Events should be based upon icalendar. At least one parser/encoder exists from @lpil although I have not checked how much support for recurring events it has.

API idea

iex> Cldr.Calendar.Format.month 2020, 4, locale: "en-US", events: icalendar_events, formatter: MySpecial.Formatter

Things to think about

• Keeping multi-day events lined up in the right place in adjacent days