Container queries - update docs

[jps]

Description

We need to document how consumers can use container queries

Split out of ##806

Tasks/Steps

• https://newskit.co.uk/theme/theming/using-a-theme/ convert to TSX page if not done already

• Create a new documentation page in themes "Creating and using themes" called "building responsive interfaces"
  Move the section Breakpoint behaviour in component defaults into this new page

• Add a further section on how to use container queries to this page.

Acceptance Criteria

As a user of the design system, it should be clear to me how I can make the most of container queries

Dependencies

To be done after #806