bug#74994: Improve Emacs iCalendar support

[Richard Lawrence]

Severity: wishlist

As discussed already a bit on emacs-devel, here:

https://lists.gnu.org/archive/html/emacs-devel/2024-10/msg00425.html

and in a write-up I posted here:

https://recursewithless.net/emacs/icalendar-parser-and-mode.org

I would like to see Emacs gain an updated, full-fledged implementation
of RFC5545, the current version of the iCalendar standard.

I have been working on this for a couple of months, and have some code
that's ready to be reviewed and discussed. I'm creating this bug to
track that discussion.