Add section backgrounds

[acouch]

We want to add this capability to our projects.

Here are some files:

• https://github.com/promet/svots/blob/27d9fb35f016cebb6c69f4ad649a445b9dd617af/config/default/layout_builder_styles.style.center.yml
• https://github.com/promet/svots/blob/27d9fb35f016cebb6c69f4ad649a445b9dd617af/config/default/layout_builder_styles.settings.yml

We need to agree on what styles do what for the "product" and how those would we updated. Ideally it would not be specific colors but those tied to the "primary", "secondary" etc of the design system.