[experimental]: PoC sitemap feature

[ahuseyn]

New Faust should have a customizable sitemap feature. The data fetching strategy is yet to be determined. The options include paginated GraphQL requests, a proxied sitemap, or an approach involving the custom-sitemap-apollo from hwptoolkit.

Tasks:

• Provide a sitemap endpoint (e.g., /sitemap.xml) in Faust.
• Provide utilities to fetch published content (posts, pages, custom post types) from WPGraphQL.