.. UNSURE HOW TO WRITE THIS AS THE ADVERT EXAMPLE IN WAGTAIL DEMO IS NOT A PARTICULARLY HELPFUL USE CASE.
When creating a page on a website, it is a common occurance to want to add in a piece of content that already exists on another page. An example of this would be a person's contact details, or an advert that you want to simply show on every page of your site, without having to manually apply it.
