noscript: add noscript tags

* hide theme-toggle and
    * go-to-top button
    when js is disabled

layouts/partials/header.html

@@ -12,6 +12,14 @@
     }
 </script>
 {{- end }}
+<noscript>
+    <style type="text/css">
+        .theme-toggle,
+        .top-link {
+            display: none;
+        }
+    </style>
+</noscript>
 <header class="header">
     <nav class="nav">
         <p class="logo">