feat(domain): add return.is-a.dev

domains/return.json

@@ -0,0 +1,10 @@
+{
+    "owner": {
+        "username": "returnxd",
+        "email": "hc_2583@naver.com"
+    },
+
+    "record": {
+        "CNAME": "returnxd.github.io"
+    }
+}