Missing style for nhsuk-list--border

[jakeb-nhs]

Bug Report

What is the issue?

There appears to be a missing CSS selector and style for the first item in a bordered list.

See the service manual for the A-Z page: https://service-manual.nhs.uk/design-system/patterns/a-to-z-page
This makes use of a list panel for each collection of conditions - the first item in each panel has a grey border above it. This comes from the following selector and style:

.nhsuk-list--border li:first-of-type {
    border-top: 1px solid #d8dde0;
    padding: 16px 0;
}

There is no such CSS present in this library, which means that when rendering an nhsuk-list--border element, the first item does not have a top border.