Add ircs as an supported protocol

InterWiki links like [ircs://irc.libera.chat/ubuntuusers #ubuntuusers]
didn’t work because ircs wasn’t interpreted as an protocol.

This commit changes the regex

r'(?:(?:https?|ftps?|file|ssh|mms|svn(?:\+ssh)?|git|dict|nntp|irc|'

to

r'(?:(?:https?|ftps?|file|ssh|mms|svn(?:\+ssh)?|git|dict|nntp|ircs?|'

which allows using both irc:// and ircs:// in InterWiki links.

inyoka/markup/lexer.py

@@ -90,7 +90,7 @@ def __init__(self, regexp, token=None, enter=None, silententer=None,
 # in use (like git or irc)
 _url_pattern = (
     # urls with netloc
-    r'(?:(?:https?|ftps?|file|ssh|mms|svn(?:\+ssh)?|git|dict|nntp|irc|'
+    r'(?:(?:https?|ftps?|file|ssh|mms|svn(?:\+ssh)?|git|dict|nntp|ircs?|'
     r'rsync|smb|apt)://|'
     # urls without netloc
     r'(?:mailto|telnet|s?news|sips?|skype|apt):)'