[exim] IRC channel for Exim

Hi All,

We have used Freenode for an IRC channel (#exim) for many years.
Recent developments are making me consider a move, possibly
to irc.libera.chat (port 6697 for SSL; #exim). The channel
exists but I've not yet gotten it confirmed as representing
the Exim project.

If anyone wants to comment, please raise a hand.
--
Cheers,
Jeremy