Update Vercel configuration for mugish.is-a.dev

- Changed CNAME to cname.vercel-dns.com for proper Vercel integration
- Added _vercel.mugish.json with TXT verification record
- Following is-a.dev Vercel setup guide

domains/_vercel.mugish.json

@@ -0,0 +1,9 @@
+{
+  "owner": {
+    "username": "MugishBeldar",
+    "email": "mugishbeldar333@gmail.com"
+  },
+  "records": {
+    "TXT": "vc-domain-verify=mugish.is-a.dev,60299edb1137634ea686"
+  }
+}

domains/mugish.json

@@ -6,6 +6,6 @@
     "email": "mugishbeldar333@gmail.com"
   },
   "records": {
-    "CNAME": "mugish-beldar.vercel.app"
+    "CNAME": "cname.vercel-dns.com"
   }
 }