use govuk header and footer components

[JC-DSIT]

Proposed changes

What changed

This change adds the GOV.UK header and footer components into the main template. This is in preparation for adding in the generic header and cleaner options to turn off gov.uk branding. This will follow in a future release.

The component settings are controlled by existing values in config/tech-docs.yml.

The option to disable GOV.UK components has also been removed from config/tech-docs.yml as this will now be required. Have added extra configurations for customising the components:

• headerContainerClasses:
• headerClasses:
• navigationContainerClasses:
• navigationClasses:

Related issue or tracking reference

You should have an open GitHub issue that this PR will fix.

• Fixes [Enhancement]: Use GOV.UK header and footer components #521
• Relates to [Enhancement]: Implement the Generic header component into an 'unbranded' version of the tech docs #516 and [Enhancement]: Allow option for custom logo #493

Checklist

Before you request approval you should confirm that:

• the pull request has a clear title with a short description about the update in the documentation
• GitHub actions all pass
• you have tested the changes with a fresh build against the latest version of the tech-docs-gem
• you have linked this PR to an issue (or explained why none exists)
• you have updated documentation if needed