Add task list component and pattern

[edwardhorsford]

Description

Adds the task list component and pattern. These are largely copied verbatim from the GOV.UK Design System, though I have made updates to refer to NHS, make the examples more relevant, or where our colour scheme differs.

As the NHS Frontend component PR hasn't been merged, this PR targets that pr in package.json. This should be removed prior to this PR being merged. For testing, you can pull this branch and run npm install and it should pick up the other work.

It's possible the component / pattern should be mentioned / listed in other bits of the app - I tried to insert it in all the places by checking where another pattern was mentioned, but it's possible I've missed places.

Component guidance

Pattern guidance

Updated tag colour examples

The tag component shows some example statuses - but these don't align with what the task list pattern uses. I've updated the two conflicting ones to align with what we and GOV.UK have.

Before	After

Related issue

This wants to be merged alongside the companion nhsuk-frontend pr adding the task list component.

Checklist

• Tested against the NHS.UK frontend testing policy (Resolution, Browser & Accessibility)
• Code follows the NHS.UK frontend coding standards
• Version number has been increased in package.json (using SEMVER)
• CHANGELOG entry
• Whats new page entry