Update list docs

Wrap in code syntax on "list" docs

app/views/govuk_publishing_components/components/docs/list.yml

@@ -66,7 +66,7 @@ examples:
     description: |
       Sets the margin on the bottom of the list element.
 
-      The component accepts a number for margin bottom from 0 to 9 (0px to 60px) using the [GOV.UK Frontend spacing scale](https://design-system.service.gov.uk/styles/spacing/#the-responsive-spacing-scale). It defaults to having a 20px margin.
+      The component accepts a number for margin bottom from `0` to `9` (`0px` to `60px`) using the [GOV.UK Frontend spacing scale](https://design-system.service.gov.uk/styles/spacing/#the-responsive-spacing-scale). It defaults to having a `20px` margin.
     data:
       margin_bottom: 9
       <<: *default-example-data