Add xmpp.net badge.

Author: ForNeVeR

README.md

@@ -1,3 +1,5 @@
 # xmpp@codingteam.org.ru
 
+[![xmpp.net score](https://xmpp.net/badge.php?domain=codingteam.org.ru)](https://xmpp.net/result.php?domain=codingteam.org.ru&type=client)
+
 Issue tracker for XMPP server on ctor