Timeline: Add text alternatives to icons in Timeline stories

[TylerJDev]

Closes https://github.com/github/primer/issues/3353

In most cases when using Timeline, consumers will keep the icons decorative, but since the stories for Timeline don't have much context, we can add text alternatives to the icons so that the meaning is conveyed properly.

Changelog

Changed

• Adds text alternatives to icons in Timeline stories

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]

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Latest commit: b341344

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[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	95.8 KB (0%)
packages/react/dist/browser.umd.js	96.19 KB (0%)