docs: Add UCEXLLY to showcase

[oluwatobiss]

Description

This PR adds UCEXLLY's Starlight documentation site to the showcase.

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Latest commit: 2652cdc

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Lighthouse	1 paths audited Performance: 100 (no change from production) Accessibility: 100 (no change from production) Best Practices: 100 (no change from production) SEO: 92 (no change from production) PWA: - View the detailed breakdown and full score reports

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[delucis]

Thanks @oluwatobiss!