For iCal Export, long lines should be wrapped
I put the iCal file from https://test.mobilizon.org/events/74120057-a122-457d-947b-490aba787afb into https://icalendar.org/validator.html and got "Line length should not be longer than 75 characters" and a link to https://icalendar.org/iCalendar-RFC-5545/3-1-content-lines.html
Related: #420 (closed), #434 (closed)