Terra show hide focusing

[adoroshk]

Summary

• A new focusRef prop was added to pass a ref to the element that should be focused after the full text is shown.
• When read by Screenreaders, upon expanding the content the screen reader starts reading the content on the newly revealed content when the component is expanded.
• Documentation was updated to include the new prop to the examples, and an explanation on how to use the new prop was added.
• Previous functionality was preserved for passivity.

Testing

This change was tested using:

• WDIO
• Jest
• Visual testing (please attach a screenshot or recording)
• Other (please describe below)
• No tests are needed

Reviews

In addition to engineering reviews, this PR needs:

• UX review
• Accessibility review
• Functional review

This PR resolves:

UXPLATFORM-9213