fix: gallery lightbox doesn't always load

Lightbox may not load in case of gallery shortcode contained within `text` field of a landing page block (v2 blocks).

Fix #2972

modules/wowchemy/layouts/partials/site_head.html

@@ -95,6 +95,14 @@
         {{ $has_gallery = true }}
       {{ end }}
     {{ end }}
+    {{ if (eq .Type "landing") }}
+      {{ range $index, $block := .Params.sections }}
+        {{ if (gt (len (findRE `\{\{< gallery` $block.content.text 1)) 0) }}
+          {{ $.Page.Store.Set "has_gallery" true }}
+          {{ $has_gallery = true }}
+        {{ end }}
+      {{ end }}
+    {{ end }}
     {{ if $has_gallery | or site.Params.require_fancybox }}
       {{ printf "<link rel=\"stylesheet\" href=\"%s\" integrity=\"%s\" crossorigin=\"anonymous\" media=\"print\" onload=\"this.media='all'\">" (printf $css.fancybox.url $css.fancybox.version) $css.fancybox.sri | safeHTML }}
     {{ end }}