updated Serbian translation credits

Author: ivanovic

data/core/about_i18n.cfg

@@ -1685,6 +1685,11 @@ sort=yes
         name = "Srecko Toroman (FreeCraft)"
         email = "sreckotoroman_AT_gmail_DOT_com"
     [/entry]
+    [entry]
+        name = "Vlastimir Krstonošić (aka: Vlastik)"
+        comment = "Current maintainer"
+        email = "krstonosicvlastimir_AT_gmail_DOT_com"
+    [/entry]
 [/about]
 
 [about]