docs: add GitHub link to README header nav

[alexgrozav]

Summary

• Sample change to test the Multica PR workflow end-to-end.
• Adds a GitHub link to the README header navigation row (alongside Homepage / Documentation / Discord).

Test plan

• Change is docs-only; no build/runtime impact.
• Confirm the new link renders correctly in the README preview.

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Latest commit: d416b7a

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Project	Deployment	Actions	Updated (UTC)
storybook-styleframe-dev	Ready	Preview, Comment	Jul 8, 2026 5:22pm
styleframe-dev	Ready	Preview, Comment	Jul 8, 2026 5:22pm