Better screen reader support of radios and checkboxes etc

[jonnystening]

The <fieldset> element should wrap grouped radios/checkboxes and use the <legend> element to define the question.

Note: also consider Switches and Button groups

See https://accessibility.blog.gov.uk/2016/07/22/using-the-fieldset-and-legend-elements/

[jonnystening]

This has been included in the latest accessible forms work

See https://github.com/WestpacCXTeam/GUI-form-checks and https://github.com/WestpacCXTeam/GUI-form-base