feat(panettone): announce newly created issues using irccat

- The new PANETTONE.IRC package contains the SEND-IRC-NOTIFICATION function,
  which opens a new TCP socket to irccat (if it's running and configured) in
  order to announce the creation of new issues.
- The IRCCATHOST and IRCCATPORT environment variables must be set for this to
  work.
- Additionally, the ISSUECHANNEL environment variable may be used to direct
  announcements at a given channel (otherwise it'll just use the first one).

Change-Id: I429a66f24d0f80ed10db173d6af7105fb1d3d023
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2077
Tested-by: BuildkiteCI
Reviewed-by: glittershark <grfn@gws.fyi>

web/panettone/src/packages.lisp

@@ -7,6 +7,10 @@
   (:use :cl :lass)
   (:export :styles))
 
+(defpackage panettone.irc
+  (:use :cl :usocket)
+  (:export :send-irc-notification))
+
 (defpackage :panettone.authentication
   (:nicknames :authn)
   (:use :cl :panettone.util :klatre)
@@ -47,5 +51,6 @@
    :id :subject :body :author-dn :issue-id :status :created-at
    :field :previous-value :new-value :acting-user-dn
    :issue-comments :num-comments :issue-events)
+  (:import-from :panettone.irc :send-irc-notification)
   (:shadow :next)
   (:export :start-pannetone :config :main))