Only index pages; add pagefind metadata based on series/tags/categories

layouts/_partials/page-metadata/item/series.html

@@ -4,7 +4,7 @@
         {{ $series = $series | append (printf `<a href="%s">%s</a>` .Permalink .LinkTitle) }}
     {{ end }}
 
-    <div class="page-metadata-section series" aria-label="{{ i18n "aria_post_meta_series" }}">
+    <div class="page-metadata-section series" data-pagefind-meta="series" aria-label="{{ i18n "aria_post_meta_series" }}">
         {{ partial "icon.html" "files" }}
         {{ delimit $series ", " | safeHTML }}
     </div>