fix: accessibility issue in tabs

[shrilakshmishastry]

Issue:

• FileTabs has given the role tab, but the tab accessibility pattern is not taken care.

Issues noticed:

• Not highlighting the tab when the file name is focused
• Not highlighting the focus state of the editor
• cross icon or close button not keyboard accessible

Fixed:

• basic tab accessibility pattern :

  1. on the tab click to focus on the first tab item initially and on the previously focused tab in case it's accessed earlier
  2. Managing Focus Within Components Using a Roving tabindex
  3. highlighting the focus on the tab and editor by default outline of the browser when focused

• on the focus of the tab, close CTA is visible and is keyboard accessible

Screen recording

Tab pattern implementation https://github.com/user-attachments/assets/6221d6dd-1050-486c-adb6-9e2e6b1420f2

Editor accessibility https://github.com/user-attachments/assets/7049baa6-762d-4015-85b6-21fd20a20f41

What kind of change does this pull request introduce?

• Accessibility fix

Checklist

• [ ] Documentation; N/A
• [x] Storybook (if applicable);
• [ ] Tests;
• [x] Ready to be merged;

This fix partially https://github.com/codesandbox/sandpack/issues/1173