help/docs css: hide navbar when printing

[6801318d8d]

I went here and tried to print the page to PDF.

But the navbar covers the text:

Please add the following style to the page:

    @media print {
        div.col-narrow.toc {
            display: none;
        }
    }

(in the meantime you can use Stylus to manually add it)

[adigitoleo]

The issue happens not only when printing but also on e.g. vertical monitors.

https://github.com/neovim/neovim/issues/27802