Make h1s bold when printing core layout content
Make h1s bold when printing core layout content

`print-base` sets heading styles for h2, h3 and h4 as bold.

For guides, h1s can appear within the page. When they are not also
bold, the structure of the content isn’t as clear.

* Make h1s bold for older layouts when printing

alphagov/static,alphagov/static,alphagov/static