refactor templates layout

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

layouts/_partials/util/get_content_by_section.html

@@ -0,0 +1,11 @@
+<!--
+    Given a top-level section title slug [blog|cv|portfolio], returns all
+    `Pages` within that top-level section.
+
+    @param  sc  The site content (`$`)
+    @param  section_slug   The slug of the section to use [blog|cv|portfolio]
+
+    @returns    Pages|nil
+-->
+
+{{- where ( ( .sc.GetPage "cv" ).Sections ) "Title" .section_title -}}