Add Vercel TXT verification record

Add Vercel verification configuration for Aditya's portfolio.

domains/_vercel.adityathakur.json

@@ -0,0 +1,13 @@
+{
+    "description": "Vercel verification for Aditya's Portfolio",
+    "repo": "https://github.com/aditya0563/portfolio",
+    "owner": {
+        "username": "aditya0563",
+        "email": "taditiya870@gmail.com"
+    },
+    "records": {
+        "TXT": [
+            "vc-domain-verify=adityathakur.is-a.dev,ed9276225e83e4aa0b19"
+        ]
+    }
+}