Fix main menu to top of page

agaric/templates/layout/region--primary-menu.html.twig

@@ -0,0 +1,21 @@
+{#
+/**
+ * @file
+ * Default theme implementation to display a region.
+ *
+ * Available variables:
+ * - content: The content for this region, typically blocks.
+ * - attributes: HTML attributes for the region <div>.
+ * - region: The name of the region variable as defined in the theme's
+ *   .info.yml file.
+ *
+ * @see template_preprocess_region()
+ *
+ * @ingroup themeable
+ */
+#}
+{% if content %}
+  <div class="is-fixed">
+    {{ content }}
+  </div>
+{% endif %}