Add changelog entry to Browser Rendering product changelog

Author: kathayl

src/content/changelog/browser-rendering/2026-01-23-robots-txt-docs.mdx

@@ -3,6 +3,11 @@ link: "/browser-rendering/changelog/"
 productName: Browser Rendering
 productLink: "/browser-rendering/"
 entries:
+  - publish_date: "2026-01-23"
+    title: "Documentation updates for robots.txt and sitemaps"
+    description: |-
+      * Added [robots.txt and sitemaps reference page](/browser-rendering/reference/robots-txt/) explaining how Browser Rendering identifies as a bot and interacts with robots.txt.
+      * Updated [automatic request headers documentation](/browser-rendering/reference/automatic-request-headers/) with User-Agent string details.
   - publish_date: "2026-01-21"
     title: "@cloudflare/puppeteer v1.0.5 released"
     description: |-