Display the nav_links in the mobile menu

[JulienPradet]

Hi! 👋

First of all, thank you for open sourcing this docs theme. We've used it in Front-Commerce's documentation and it is really great!

However, I've noticed that there's an issue when displaying the nav_links on mobile. They should appear above the sidebar but are hidden behind the header. It is displayed correctly though when you start in desktop mode and resize to mobile.

This can be seen in Apollo Docs : https://www.apollographql.com/docs/

We've made a fix on our side, but I'm not sure that the PR would be OK for you since our fix uses flexbox and I've noticed that it does not seem to appear in your codebase. If it's OK for you though, I could make a PR later on.

Our fix: front-commerce/developers.front-commerce.com@c122803
A working preview: https://deploy-preview-18--elastic-austin-cf9d40.netlify.com/docs/

[JulienPradet]

Oops, nevermind for my fix. It has compatibility issues. I'll try to come up with a different one, but the bug is still relevant.