chore: Add serbian language config (#6923)

Author: beny996

apps/site/i18n/config.json

@@ -229,6 +229,16 @@
     "enabled": false,
     "default": false
   },
+  {
+    "code": "sr",
+    "localName": "Srpski",
+    "name": "Serbian",
+    "langDir": "ltr",
+    "dateFormat": "DD.MM.YYYY",
+    "hrefLang": "sr",
+    "enabled": false,
+    "default": false
+  },
   {
     "code": "sv",
     "localName": "Svenska",