refactor templates layout

@see https://gohugo.io/templates/new-templatesystem-overview/

layouts/_partials/single/footer-scripts.html

@@ -0,0 +1,56 @@
+{{- /*
+  Renders a single item's required footer JS scripts.
+
+  @params sc Site context.
+  @params pc Page context.
+  */
+-}}
+
+
+<!-- Validation -->
+
+{{- if ( not ( isset . "sc" ) ) -}}
+  {{- errorf "No site context passed" -}}
+{{- end -}}
+
+{{- if ( not ( isset . "pc" ) ) -}}
+  {{- errorf "No page context passed" -}}
+{{- end -}}
+
+{{- if ( and ( .pc.HasShortcode "chart" ) ( not ( .pc.Page.Resources.GetMatch "charts-init" ) ) ) -}}
+  {{- errorf "No 'chart-init' page resource defined (%q)" .pc.Page.File.Path -}}
+{{- end -}}
+
+
+<!-- Rendering -->
+
+{{ if .pc.Params.locations }}
+    <script>
+    {{-
+        (
+            partialCached
+            "scripts/show_post_locations_on_map.js"
+            ( dict
+                "pc" .pc
+                "locations_data" .sc.Site.Data.locations
+                "locations" .pc.Params.locations
+            )
+            .pc.Params.locations
+        ) | safeJS
+    -}}
+    </script>
+{{ end }}
+
+{{ if .pc.HasShortcode "chart" }}
+  {{- $configJs := ( .pc.Page.Resources.GetMatch "charts-init" | fingerprint ) -}}
+    <script>
+    {{-
+        (
+            partialCached
+            "scripts/charts.js"
+            $configJs
+            $configJs
+        ) | safeJS
+    -}}
+    </script>
+{{ end }}