15833 make navbar sticky at top

netbox/templates/base/layout.html

@@ -47,7 +47,7 @@ Blocks:
     </aside>
 
     {# Top menu #}
-    <header class="navbar navbar-expand-md d-none d-lg-flex d-print-none">
+    <header class="navbar navbar-expand-md sticky-top d-none d-lg-flex d-print-none">
       <div class="container-fluid">
 
         <div class="navbar-nav flex-row align-items-center order-md-last">