Add documentation for Shared Catalog

[evillique]

Summary

Checklist

• Delete items not relevant to your PR
• URL changes should add a redirect to the old URL via https://github.com/ClickHouse/clickhouse-docs/blob/main/docusaurus.config.js
• If adding a new integration page, also add an entry to the integrations list here: https://github.com/ClickHouse/clickhouse-docs/blob/main/docs/integrations/index.mdx

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Name	Status	Preview	Comments	Updated (UTC)
clickhouse-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 4, 2025 9:45am
clickhouse-docs-jp	🔄 Building (Inspect)	Visit Preview	💬 Add feedback	Jun 4, 2025 9:45am
clickhouse-docs-ru	❌ Failed (Inspect)			Jun 4, 2025 9:45am
clickhouse-docs-zh	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 4, 2025 9:45am