Add irssi theme

The theme is intended to closely resemble the default Irssi look and
feel, with minimum visual clutter in UI elements, roster and occupants
lists are simplistic, similar to nicklist.pl Irssi script output.

Based on "original" theme.

themes/irssi

@@ -0,0 +1,131 @@
+[colours]
+bkgnd=default
+titlebar=blue
+titlebar.text=white
+titlebar.brackets=cyan
+titlebar.unencrypted=red
+titlebar.encrypted=white
+titlebar.untrusted=yellow
+titlebar.trusted=white
+titlebar.online=white
+titlebar.offline=white
+titlebar.away=white
+titlebar.chat=white
+titlebar.dnd=white
+titlebar.xa=white
+statusbar=blue
+statusbar.text=white
+statusbar.time=white
+statusbar.brackets=cyan
+statusbar.active=cyan
+statusbar.new=red
+main.text=white
+main.text.me=white
+main.text.them=white
+main.splash=cyan
+main.help.header=white
+main.time=white
+input.text=white
+subscribed=green
+unsubscribed=red
+otr.started.trusted=green
+otr.started.untrusted=yellow
+otr.ended=red
+otr.trusted=green
+otr.untrusted=yellow
+online=lightcyan
+away=cyan
+chat=green
+dnd=red
+xa=cyan
+offline=cyan
+incoming=yellow
+mention=yellow
+trigger=yellow
+typing=yellow
+gone=yellow
+error=red
+roominfo=yellow
+roommention=yellow
+roommention.term=yellow
+roomtrigger=yellow
+roomtrigger.term=yellow
+me=bold_white
+them=white
+roster.header=yellow
+roster.chat=green
+roster.online=green
+roster.away=cyan
+roster.xa=cyan
+roster.dnd=red
+roster.offline=red
+roster.chat.active=green
+roster.online.active=green
+roster.away.active=cyan
+roster.xa.active=cyan
+roster.dnd.active=red
+roster.offline.active=red
+roster.chat.unread=green
+roster.online.unread=green
+roster.away.unread=cyan
+roster.xa.unread=cyan
+roster.dnd.unread=red
+roster.offline.unread=red
+roster.room=green
+roster.room.unread=green
+roster.room.mention=green
+roster.room.trigger=green
+occupants.header=yellow
+receipt.sent=red
+
+[ui]
+titlebar.position=1
+mainwin.position=2
+statusbar.position=3
+inputwin.position=4
+occupants=false
+occupants.size=15
+occupants.indent=0
+time.console=%H:%M
+time.chat=%H:%M
+time.muc=%H:%M
+time.config=%H:%M
+time.private=%H:%M
+time.xmlconsole=%H:%M:%S
+time.statusbar=%H:%M
+presence=true
+roster.offline=false
+roster.empty=false
+roster.by=presence
+roster.order=presence
+roster.unread=before
+roster.priority=false
+roster.size=15
+roster.wrap=false
+roster.header.char=none
+roster.contact.char=none
+roster.contact.indent=0
+roster.resource=false
+roster.presence=false
+roster.status=false
+roster.contacts=true
+roster.unsubscribed=false
+roster.rooms=true
+roster.rooms.order=unread
+roster.rooms.unread=after
+roster.rooms.pos=last
+roster.rooms.by=service
+roster.rooms.char=#
+roster.rooms.private.char=/
+roster.private=room
+roster.private.char=+
+roster.count=unread
+roster.count.zero=true
+privileges=true
+presence=true
+intype=true
+enc.warn=true
+tls.show=true
+console.muc=none
+console.chat=none
+console.private=none