USWDS-Site - Feature: Add modal accessibility guidance for trapping focus

[amycole501]

Is your feature request related to a problem? Please describe.

The modal component code does trap the users' focus inside the modal upon activation.

However there is no callout to ensure that it is a key element to accessibility compliance for that component.

Describe the solution you'd like

On the modal page https://designsystem.digital.gov/components/modal/ under "accessibility" please add the following:

Ensure keyboard focus is trapped inside the modal. When using a keyboard to test the modal, ensure focus does not move to the page behind it.

Describe alternatives you've considered

The modal accessibility tests will expand on this guidance but it is important to call out keyboard focus for the modal to highlight its importance.

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct.
• I checked the current issues for duplicate feature requests.