Gov-uk-dashboards

- update header component - strong_class applied to div, as otherwise box is always fixed width

Add class to override background colour of container class

- Update header component to use class for strong component
- Add fix-width class to CSS

What's Changed
* Add style to message banner by tom-clarke-dluhc in https://github.com/communitiesuk/pkg_gov_uk_dashboards/pull/163


**Full Changelog**: https://github.com/communitiesuk/pkg_gov_uk_dashboards/compare/v9.38.0...v9.39.0

Add column layout CSS class

- Add text-no-transform class