Document headers inside of labels - when to use and when not to use

[humancompanion-usds]

Description

The va-radio and va-checkbox-group components support the option of using a header inside their top-level label:
https://design.va.gov/storybook/?path=/docs/uswds-va-radio--label-header
https://design.va.gov/storybook/?path=/docs/uswds-va-checkbox-group--label-header

It's also an option in v1. We need to document this option in va-checkbox-group

Details

Add details from Jeana on when and when not style a label as a header. This will also need to touch on fieldsets, legends, aria-labelledby, et. al. Ideally this would also show annotated examples and connect to templates for the One Thing Per Page content principle that we are using now within our forms.

Tasks

• Update va-checkbox-group component documentation for design.va.gov
• Update accessibility guidance on labels inside of headers
• Add annotated examples of various "One thing per page" scenarios in Template - Forms
• Once documentation is approved, publish to design.va.gov

Acceptance Criteria

• Guidance is published on design.va.gov

[jeana-adhoc]

Just adding a note here that I think I might be taking care of this when I merge this draft documentation into the Accessibility Cookbook.

We can point to the cookbook from various VADS pages as needed.