Document how to use this theme

Hello Kevin,

The "navbar" variable is by default defined with the content of the "header_navbar" region in the "page.html.twig" and "page--404.html.twig" templates.

If you have declared a child theme, make sure that this region exists in your new theme.

In an evolution, we can also consider setting a default value if the region does not exist.

You can contact me via Slack if necessary.

Defining the regions did the trick ! Cheers.

added information to the readme about creating a subtheme

Hello @kgaut,

Thanks for the additional documentation.

I gave you a brief feedback in the Merge Request.

Cheers,