Add VerticalStepper component to docs with custom syntax

[Blargian]

Summary

• Adds ability to use custom syntax in markdown <VerticalStepper></VerticalStepper> around content which will render H2 sections as steps of the Click-UI VerticalStepper component.

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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[Blargian]

Working but not working... Docusaurus reports broken anchors for the headers inside of <VerticalStepper></VerticalStepper>. Cannot use useBrokenLinks().collectAnchor("") as it needs to be done in the React component but anchor check fails at build time. Adding <a> to the page at transform time also didn't help. Maybe facebook/docusaurus#11101 could be of some use?

Everything is possible when you struggle long enough

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Name	Status	Preview	Comments	Updated (UTC)
clickhouse-docs	✅ Ready (Inspect)	Visit Preview		May 6, 2025 1:20pm

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[gingerwizard]

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