Update domain owner information in mj.json

domains/mj.json

@@ -0,0 +1,9 @@
+{
+  "owner": {
+    "username": "mj-youn",
+    "email": "yun0244@naver.com"
+  },
+  "records": {
+    "CNAME": "mj-youn.github.io"
+  }
+}