Fix rss.xml.js field: publishDate to pubDate

src/pages/rss.xml.js

@@ -23,7 +23,7 @@ export const get = async () => {
 			link: getPermalink(post.slug, 'post'),
 			title: post.title,
 			description: post.description,
-			publishDate: post.publishDate,
+			pubDate: post.publishDate,
 		})),
 	});
 };