Support an easier way to use a full-width layout to reflect common GOV.UK and service page patterns

[rivalee]

What

Make it easier for users to change the page layout to a full width layout – eg the GOV.UK topic page uses a full-width layout https://www.gov.uk/browse/benefits and so do most service start pages, such as Notify: https://www.notifications.service.gov.uk/

Image above is a screenshot of Notify (https://www.notifications.service.gov.uk/) using a full-width page layout.

Why

So that users can more easily change their Prototype Kit page layout, to reflect common GOV.UK and service page patterns

Done when

The Prototype Kit enables users to more easily change the page layout

[joelanman]

this could make a good page template, as a plugin