fix(theme): do not show tab content when tabbing over it; show after selection only

[mturoci]

Motivation

Improve a11y for Tabs component.

Test plan

manual - Voiceover on MacOS.

Screen.Recording.2022-10-02.at.9.53.34.AM.mov

Tab content is only shown after selection (hitting enter).

Compare:

• https://docusaurus.io/docs/markdown-features/tabs
• https://deploy-preview-8161--docusaurus-2.netlify.app/docs/markdown-features/tabs

Related issues

Closes #8063

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[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
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/docs/installation	🟠 71	🟢 100	🟢 100	🟢 100	🟢 90	Report

[mturoci]

I have signed the CLA:

But somehow the PR checks didn't run again. Any ideas on how to resolve this?

Edit: They ran, but some 2h later so all good.

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[Josh-Cena]

@backwardok Could you take a look at https://deploy-preview-8161--docusaurus-2.netlify.app/docs/markdown-features/tabs/ and confirm if that's your desired UX?

[backwardok]

@Josh-Cena this looks good! There's a change in behavior for keyboard-only users, but with the focus outline I think this should still be understandable on how to activate the tabs.

@mturoci Thank you for fixing this!

[mturoci]

Hi @Josh-Cena is there anything I can do to get this PR merged in? (e.g. any required code changes)

[slorber]

Thanks @mturoci that looks to work as intended 👍

Was wondering, shouldn't we announce the tab content after selecting a new tab? similarly to aria-live used in #8174 ?

Let's handle that in a separate PR because I have no idea on which DOM element such attribute could be added 😅

[backwardok]

Hi @slorber ! I wouldn't recommend announcing the tab content after selecting a new tab. As long as the user knows that the tab changed (which they should get from the change in aria-selected for the tab), they should know that the tab content should also have changed and access it when they want to.