Add custom headers for robots.txt and sitemap.xml in Vercel configuration

- Added Content-Type headers for robots.txt and sitemap.xml to ensure correct content delivery.
- Updated rewrites to exclude these files from being redirected to index.html.

Author: m-brtn

docs-site/static/robots.txt

@@ -0,0 +1,5 @@
+User-agent: *
+Disallow: /search
+Allow: /
+
+Sitemap: https://docs-python-sdk.vaiz.com/sitemap.xml

docs-site/vercel.json

@@ -4,9 +4,29 @@
   "framework": "docusaurus",
   "installCommand": "npm install",
   "trailingSlash": false,
+  "headers": [
+    {
+      "source": "/robots.txt",
+      "headers": [
+        {
+          "key": "Content-Type",
+          "value": "text/plain"
+        }
+      ]
+    },
+    {
+      "source": "/sitemap.xml",
+      "headers": [
+        {
+          "key": "Content-Type",
+          "value": "application/xml"
+        }
+      ]
+    }
+  ],
   "rewrites": [
     {
-      "source": "/:path*",
+      "source": "/:path((?!robots\\.txt|sitemap\\.xml|_next|api|static|assets|img|.*\\..*).*)",
       "destination": "/index.html"
     }
   ]