[Component amendment]: Notifications, enable lists in notification message

## Component/pattern to amend

[Notification](https://vanillaframework.io/docs/patterns/notification)

## Visual


## Context

The Notification component doesn't expect lists, and while it works, it generates invalid markup, because it only expects text.
I'd like to display error notifications for payment issues, that could have multiple reasons or ways to resolve, breaking up these for the users would improve readability. I wanted to know if there are any guidance on the preferred size of notification messages.

Start with the Notification pattern documentation at vanilla-framework.io/docs/patterns/notification and inspect the component entry point and its existing markup guidance. Confirm how lists should be represented without invalid markup, and document or demonstrate the preferred notification message size when the change is complete.

Written by the indexing model from the issue text.