Enable scrollable responsive nav bar

Fixes #9007 in a hopefully decent way

dist/css/bootstrap.css

@@ -2870,6 +2870,16 @@ button.close {
   margin-bottom: 0;
 }
 
+@media (max-width: 768px) {
+  .nav-collapse-scrollable {
+    max-height: 360px;
+    margin-bottom: 15px;
+    overflow-x: hidden;
+    overflow-y: scroll;
+    -webkit-overflow-scrolling: touch;
+  }
+}
+
 .navbar-brand {
   display: block;
   max-width: 200px;