Add storybook-addon-performance-panel

[fredvisser]

Pull Request

🤨 Rationale

Adds the @github-ui/storybook-addon-performance-panel to Storybook. This addon provides a real-time "⚡ Performance" panel in Storybook showing frame timing, input responsiveness, layout stability, memory usage, and other browser-level metrics for every story.

👩‍💻 Implementation

• Installed @github-ui/storybook-addon-performance-panel as a dev dependency in packages/storybook/package.json.
• Registered the addon in .storybook/main.js using the ./universal subpath (appropriate for non-React / HTML/Web Components frameworks). The string is used directly rather than wrapped in getAbsolutePath(), since getAbsolutePath resolves <pkg>/package.json and the subpath export does not have a nested package.json.
• Added the addonPerformancePanel() decorator to preview.js so it applies to all stories automatically.

🧪 Testing

• Verified Storybook starts without errors and the "⚡ Performance" panel appears.

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.

[jattasNI]

Do you have a specific use case or workflow in mind for adding this? It certainly looks cool. But our controls tend to be very static so most of the metrics should look boringly good. What do we hope to get from adding it?

There's not much harm in adding it, though the Storybook deps tend to have vulnerabilities and require manual intervention to update them, so fewer is generally better.