Add example PageLayout stories for responsive sidebar patterns

[mperrotti]

Relates to https://github.com/github/primer/issues/3108

Changelog

These changes only affect stories. There are no changes that require a changeset.

Merge checklist

• [ ] Added/updated tests
• [x] Added/updated documentation
• [x] Added/updated previews (Storybook)
• [ ] Changes are SSR compatible
• [x] Tested in Chrome
• [x] Tested in Firefox
• [x] 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[bot]]

⚠️ No Changeset found

Latest commit: 91d2137dbe69c58ae208fc34a8327fb2fcac1f35

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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[github-actions[bot]]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	89.62 KB (0%)
packages/react/dist/browser.umd.js	89.93 KB (0%)