Google News sitemap.xml extensions within sitemaps export function in app dir

[ptpittman]

Goals

1. Use next.js 14's sitemap export function to create a Google News compatible sitemap, by adding some extra supported fields to the return
2. Allow for extensibility to sitemap export based on stable existing schemas

Non-Goals

1. Create arbitrary non-defined exports within sitemap export.

Background

Google documents a specific stable set of News-based extensions to the Sitemap schema (under news:news container) which they use for better indexing news media for their news section.

While I could use another tool like next-sitemap to generate this, it would be useful for a unified approach if there was a way to optionally include these fields (or perhaps other extensions, google and non, in a more extensible approach) using the great new sitemap() export feature in the app dir.

Proposal

To me it seems it would be clean enough to add an extra news: {...} object within each entry object that would work identically to how openGraph schema extensions are implemented in the generateMetadata() export. Other Google extensions (image, news) could work similarly.

Happy to contribute if needed, though haven't yet on this codebase!