add cname record for github pages

domains/mio.json

@@ -2,6 +2,8 @@
   "owner": {
     "username": "ShirakawaMio",
     "email": "mio.liu.rx@gmail.com",
-    "github": "ShirakawaMio"
   },
+  "records": {
+    "CNAME": "shirakawamio.github.io"
+  }
 }