add fail2ban jail for archwiki role

roles/archwiki/templates/fail2ban.jail.j2

+#
+# {{ansible_managed}}
+#
+
+[wiki-nginx-dos]
+enabled = true
+filter = nginx-dos
+action = iptables-multiport[name=ReqLimit, port="http,https", protocol=tcp]
+logpath = /var/log/nginx/wiki.archlinux.org/access.log
+# 400 pages in 30 minutes
+findtime = 1800
+bantime = 1d
+maxretry = 400