2.0.5: Ship a sitemap.xml provider in the plugin scaffold

New plugins created via gp247:make-plugin now get Seo.php (a
sitemapUrls() stub returning [] with a commented example) and a
matching registration block in Provider.php out of the box, so plugin
authors integrate with gp247/front's sitemap.xml registry (US-PLG-007,
seo_plugin-sitemap-extension ADR in the s-cart aidlc-docs repo) without
having to read the News plugin's source to discover the pattern.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>