fix(PageHeader): add role prop and aria-label in top-level element

[francinelucca]

Closes https://github.com/github/primer/issues/3466

Changelog

New

• Adds role prop in PageHeader
• Adds PageHeader tests to assert added functionality

Changed

• Adds role="banner" and aria-label to applicable instances of PageHeader in Storybook and tests
• Sets aria-label attribute in PageHeader's "root" element mapped to the supplied aria-label
• Adjusts PageHeader's aria-label docs description to reference "landmark" instead of inaccurate "main landmark"
• Includes aria-label prop in PageHeader Playground story

Removed

N/A

Rollout strategy

• Patch release
• Minor release
• Major release; if selected, include a written rollout or migration plan
• None; if selected, include a brief description as to why

Testing & Reviewing

Integration Test: https://github.com/github/github/pull/341930

• Check preview Playground story:
  • Notice in the DOM the "banner" role in the top-level Box element and the aria-label that maps to the title prop
  • Change title prop in playground and notice the aria-label change in the DOM as well
• Check preview Default story:
  • Notice in the DOM the "banner" role in the top-level Box element and the aria-label

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Storybook)
• Changes are SSR compatible
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge
• (GitHub staff only) Integration tests pass at github/github (Learn more about how to run integration tests)

[changeset-bot]

🦋 Changeset detected

Latest commit: 863c1e1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/react	Minor

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[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	97.42 KB (-0.07% 🔽)
packages/react/dist/browser.umd.js	97.71 KB (-0.01% 🔽)

[primer-integration]

👋 Hi from github/github! Your integration PR is ready: https://github.com/github/github/pull/341930

[camertron]

LGTM 🫡