Add TXT record for domain verification

domains/artem-testlab.json

@@ -4,6 +4,7 @@
     "email": "ravonmy@gmail.com"
   },
   "records": {
-    "CNAME": "ravonmy-creator.github.io"
+    "CNAME": "ravonmy-creator.github.io",
+    "TXT": "rc.graphpad.com:domain-verification=NSv_-k6LyVkmkLCVC63XHw"
   }
 }