Restructure theme, use autoloader

templates/index.php

@@ -0,0 +1,14 @@
+<?php App\template_part('partials/page-header'); ?>
+
+<?php if (!have_posts()) : ?>
+  <div class="alert alert-warning">
+    <?php _e('Sorry, no results were found.', 'sage'); ?>
+  </div>
+  <?php get_search_form(); ?>
+<?php endif; ?>
+
+<?php while (have_posts()) : the_post(); ?>
+  <?php App\template_part('partials/content-' . (get_post_type() != 'post' ? get_post_type() : get_post_format())); ?>
+<?php endwhile; ?>
+
+<?php the_posts_navigation(); ?>