Document styling pattern for UI refactoring

# Spike

We need to agree upon which CSS styling pattern we want to use as there are [numerous options](https://blog.logrocket.com/best-styling-options-nextjs/)

# Patterns to consider

## Styled components

Example libraries: [Emotion](https://emotion.sh/docs/introduction), [styled-jsx](https://github.com/vercel/styled-jsx)

Pros:
- Makes components more self-contained
Cons:
- Code duplication

## Utility classes

Example library: [Tailwind](https://tailwindcss.com/docs/utility-first)

Pros:
- Reusable css
Cons:
- Less straightforward,

## Other

We might mix the two, use global stylesheets in addition.

## Output

Styling pattern is chosen and documented in UI guidelines.