fix: testing headers

vercel.json

@@ -22,6 +22,27 @@
         }
       ]
     },
+    {
+      "source": "/plus/",
+      "headers": [
+        {
+          "key": "Access-Control-Allow-Origin",
+          "value": "https://plus.excalidraw.com"
+        },
+        {
+          "key": "X-Content-Type-Options",
+          "value": "nosniff"
+        },
+        {
+          "key": "Feature-Policy",
+          "value": "*"
+        },
+        {
+          "key": "Referrer-Policy",
+          "value": "origin"
+        }
+      ]
+    },
     {
       "source": "/:file*.woff2",
       "headers": [