Antimatter : top hamburger menu instead of sidebar?

Hi,
I'm trying to get a simple top hamburger menu on small device, instead of the current sidebar (which is the only thing I don't find so sexy with antimatter theme). Is someone can briefly tell me where I should start to get into it ? I've also opened an issue about that sidebar menu content at https://github.com/getgrav/grav-skeleton-onepage-site/issues/9. Thanks !