Make events editable

Sometimes Stasht gets the details of the events wrong, or doesn’t include them. For example, a lot of events taken from IG show up in the calendar as “All Day” when they actually have a designated time. It would be nice to be able to edit the details of an event after it’s automatically added. Similarly, add the ability to delete a calendar event (sometimes it duplicates events, or adds other events from a post that lists multiple).