fix(unity-bootstrap-theme): add tabindex=0 to tab contents for access…

[tbutterf]

…ibility

UDS-1637

Description

This goes back to WS2-2004, which goes back to SCHWEB-1172. Kathy had indicated that we needed to comply with WCAG on tabbed panels, and for the most part this had happened. But, UDS hadn't added tabindex="0" to the tab body content, which is recommended in the WCAG standards https://www.w3.org/WAI/ARIA/apg/patterns/tabs/examples/tabs-automatic/#accessibilityfeatures. So, I have added that here.

Links

• Unity reference site
• JIRA ticket
• Unity Design Kit

FOR APPROVERS

• Percy build approval

Checklist

• [x] Unity project successfully builds from root yarn install & yarn build
• [x] Commits do not contain multiple scopes
• [x] Add/updated examples
• [x] Add/updated READMEs/docs
• [x] No new console errors
• [x] Accessibility checks

Browsers

• [x] Chrome
• [x] Safari
• [x] Firefox
• [x] Edge

Images