feat(nx-dev): add nx-blog sitemap to root sitemap index (#35363) Add sitemap for blog: - https://deploy-preview-35363--nx-dev.netlify.app/sitemap.xml - https://deploy-preview-35363--nx-dev.netlify.app/sitemap-2.xml (rewritten to blog) ## Current Behavior The root sitemap.xml index references only /sitemap-1.xml (Framer via edge-function proxy) and /docs/sitemap-index.xml (astro-docs). Blog posts published by nx-blog (BLOG_URL) are not advertised to crawlers through the root nx.dev sitemap. ## Expected Behavior The root sitemap index additionally references /sitemap-2.xml, which is served by a consolidated `additional-sitemaps.ts` edge function that proxies the per-source sitemaps: /sitemap-1.xml -> /sitemap.xml /sitemap-2.xml -> /blog/sitemap.xml URLs in the upstream XML are rewritten from the source origin to nx.dev. The previous per-source edge functions (framer-sitemap.ts, blog-sitemap.ts) are replaced by the single additional-sitemaps.ts to match the "additionalSitemaps" language used in the Next.js sitemap config. ## Related Issue(s) Fixes DOC-486 ## Current Behavior ## Expected Behavior ## Related Issue(s) Fixes #