Add new review app example pages in preparation for external audit

[querkmachine]

What

Add new full page examples to the Frontend review app so that external auditors can test our styles, components and patterns in the context of full, functional pages.

Why

We produced lots of new full page examples for our last external audit (https://github.com/alphagov/govuk-frontend/pull/3503), however these remained separated from the main project and are now outdated, and likely incompatible with the architectural and tooling changes made in subsequent versions of Frontend.

This time around we intend to make these examples permanent additions to the review app, so that they can be remain contemporary with Frontend.

We will only be recreating a subset of the examples, based on which ones were flagged for improvement in the last audit [internal document].

Who needs to work on this

• Developers

Who needs to review this

• Developers
• Content writers(?)
• Designers(?)
• Accessibility specialist(?)

Done when

• [ ] Examples from the previous audit have been recreated in the current review app
  • [ ] 'Visit the UK on a business trip' (step-by-step navigation)[^1]
  • [x] 'Make a payment' (inputs with prefixes/suffixes and error validation)
• [x] Existing examples have been updated
  • [x] Start page / 'Apply for a UK passport': Add headings to tab panels for mobile
  • [x] 'Update your account details': Add second password input
• [x] An example using the prototype service header component has been created (this will be within the service header PR and provided as a separate URL)

[^1]: We decided not to re-audit the step-by-step navigation, as this component is owned by the GOV.UK team rather than the Design System and hasn't been substantially altered since the last audit.

[querkmachine]

The service header component example is located here: https://govuk-frontend-pr-4950.herokuapp.com/full-page-examples/manage-company-information