Add additional GOV.UK full page examples to review app

[36degrees]

What

In #2089, there are two additional full page examples which we think are going to continue to be useful:

• Coronavirus campaign page
• Search results page

As #2089 is a throwaway branch which will not be merged, split these two examples out and add them to the review app.

Why

These examples have been useful when exploring how new link styles might look on the sorts of link-heavy pages you might find on GOV.UK

Who needs to know about this

Chris, Hanna

Further detail

We probably need to think about whether there's a better way to add the extra CSS required for these pages, for example so that it can use the Sass variables and mixins.

Done when

• Coronavirus campaign example page added
• Search results example page added