Add Users/Authors sitemap

[GaryJones]

Add a sitemap for site authors/users who have published posts.

Requirements

• Include users who have at least one published post
• Single paginated sitemap: /sitemap-author.xml, /sitemap-author-2.xml (if needed)
• Implement AuthorContentProvider extending PaginatedContentProviderInterface
• Settings to enable/disable in admin UI
• Filter to exclude specific users: msm_sitemap_exclude_author

URL Structure

/sitemap-author.xml
/sitemap-author-2.xml (if > 2000 authors)

Implementation Notes

This should follow the same pattern as the taxonomy sitemap implementation, using the PaginatedContentProviderInterface for non-date-based content.

References

• WordPress core includes users in sitemaps via WP_Sitemaps_Users
• Only users with published posts should be included
• Respect user privacy settings (users can opt-out)