Add feed link to header

lib/Render/Head.rakumod

@@ -43,6 +43,9 @@ sub generate-head(BlogMeta:D $meta, $title?, $description?) is export {
             :href</resources/admonitions.css>;
         # Tell dark reader that we'll behave
         meta :name<color-scheme>, :content<light dark>;
+        # Tell feed readers about our feed
+        link :rel<alternate>, :type<application/atom+xml>, :title($meta.title),
+            :href</feed.xml>;
     ]
 }