Add guidelines for breadcrumbs

If we implement breadcrumbs as additional navigation https://github.com/AlmaLinux/wiki/pull/551, it should be documented and added to the wiki for the future new pages. There's a [Contribute to Documentation](https://wiki.almalinux.org/Contribute-to-Documentation.html) page that contains most of our policies/templates we try to stick to. It sounds as a right place to add about breadcrumbs