Add underline prop to BranchName component

[TylerJDev]

Adds the ability to have underlines in BranchName when being used as a link (<a>). The method to add underlines would be the same as in the Link component, and the same rules would apply in order for the underline to appear.

Context: https://github.com/github/accessibility-audits/issues/10090#issuecomment-2605230228

Changelog

New

• Adds prop inline to BranchName component
• Adds to documentation

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

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: 2b5dadf

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]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	104.23 KB (-0.02% 🔽)
packages/react/dist/browser.umd.js	104.67 KB (+0.11% 🔺)