pass through the tudor crown option in the account-header layout

[oscarduignan]

This change was prompted by updates to the design-system but you can test this in a prototype by doing the following steps:

1. cd hmrc-frontend
2. npm run build:package
3. mkdir ../example-prototype
4. cd ../example-prototype
5. npx govuk-prototype-kit@latest create
6. nvm install --lts && npm install
7. npm install govuk-frontend@4
8. npm install ../hmrc-frontend/package
9. edit app/views/index.html and make it extend the account header layout and set it to use tudor crown

   {% extends "hmrc/layouts/account-header.html" %}
   {% set hmrcAccountHeader = { useTudorCrown: true } %}

10. npm run dev
11. open http://localhost:3000
12. you should see the tudor crown in the header (and if you toggle useTudorCrown to false and refresh it will go away)