UI: Upgrade nav-global to web-assets v2 component

Upgrade nav-global markup and styles to web-assets v2's pre-compiled
nav-global component to improve visual consistency with other sites.

templates/custom/header.tmpl

@@ -52,6 +52,13 @@
     display: none;
   }
 
+  /* Navigation */
+  @media(min-width: 1200px) {
+    .nav-global .nav-global-container {
+      max-width: 1170px;
+    }
+  }
+
   /* Repository page. */
   .repository .file-view.markdown a {
     color: var(--color-primary);