Style the new footer middle slot

[fionamorrison23]

User story

As a site owner
I want an additional slot available in the footer
And I want the styling applied so the space between slots is a per the design
So that I can add a list of links or other content in this region

Description

We added an additional middle slot to the footer in the last release. The front end styling wasn't done and it's been noted there is no space between the existing middle slots and the new one.

Design

Specifically Vertical + 
Horizontal Centre
https://www.figma.com/design/nXTZFR1mKPLExtEbYtazzD/CivicTheme%3A-Design-System-v1.9.0?node-id=2976-41730&t=ElPO4htxZhaXebPT-0

Acceptance criteria

Given I am an anonymous user
When I view a footer that has the additional middle slot
Then the styling matches the design, allowing for space between the new slot and the slots above