A basic component for the app header. The header outputs breadcrumbs via the `sections` prop (required) and access to the activity panel. It also sets the document title.
*`sections` (required): Used to generate breadcrumbs. Accepts a single items or an array of items. To make an item a link, wrap it in an array with a relative link (example: `[ '/analytics', __( 'Analytics', 'wc-admin' ) ]` ).