Docs: Add Yarn to About Section

What I did

Add a tab for yarn in the About section.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

[ ] stories
[ ] unit tests
[ ] integration tests
[ ] end-to-end tests

Manual testing

Run a sandbox for template, e.g. yarn task --task sandbox --start-from auto --template react-vite/default-ts
Open Storybook in your browser
Access Settings > About

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

[ ] Add or update documentation reflecting your changes
[ ] If you are deprecating/removing a feature, make sure to update MIGRATION.MD

Checklist for Maintainers

[ ] When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts
[ ] Make sure this PR contains one of the labels below:

Available labels
- `bug`: Internal changes that fixes incorrect behavior. - `maintenance`: User-facing maintenance tasks. - `dependencies`: Upgrading (sometimes downgrading) dependencies. - `build`: Internal-facing build tooling & test updates. Will not show up in release changelog. - `cleanup`: Minor cleanup style change. Will not show up in release changelog. - `documentation`: Documentation **only** changes. Will not show up in release changelog. - `feature request`: Introducing a new feature. - `BREAKING CHANGE`: Changes that break compatibility in some way with current major version. - `other`: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

_core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>_

Greptile Summary

This PR adds support for the Yarn package manager in the UpgradeBlock component within Storybook's About section.

Added 'yarn' tab alongside existing 'npm' and 'pnpm' options in code/core/src/manager/components/upgrade/UpgradeBlock.tsx
Updated state handling to include 'yarn' as a package manager option
Modified upgrade command rendering to display correct command for Yarn
Enhanced user interface to allow selection of preferred package manager for upgrades

storybookjs / storybook