Public IRC chat channels moved to libera

[nia <nia%NetBSD.org@localhost>]

Due to the unfortunate situation regarding changes in administration on
freenode.net, and the resulting chaos, we have decided to move the public
NetBSD IRC channels from freenode to irc.libera.chat.

This includes:

#NetBSD - general discussion
#netbsd-code - development discussion
#pkgsrc - pkgsrc (primarily development) discussion

You can find information on connecting to Libera
at https://libera.chat/

Thanks,

nia