Add crawl-delay to robots.txt (#3009)

* Add crawl-delay to robots.txt

* fix

Author: Nutomic

Diff for: src/server/handlers/robots-handler.ts

@@ -16,5 +16,5 @@ export default async ({ res }: { res: Response }) => {
   Disallow: /password_change
   Disallow: /search/
   Disallow: /modlog
-  `);
+  Crawl-delay: 60`);
 };