fix: restore robots.txt identity rewrite to prevent SPA catch-all override

Without the identity rewrite, requests for robots.txt fall through to the
catch-all rewrite and serve index.html instead of the static file, breaking
SEO crawlability.

Author: amondnet

example/angular/vercel.ts

@@ -18,6 +18,7 @@ export const config: VercelConfig = {
     ),
   ],
   rewrites: [
+    routes.rewrite('/robots.txt', '/robots.txt'),
     routes.rewrite('/favicon.ico', '/favicon.ico'),
     routes.rewrite('/(.*)', '/index.html'),
   ],