Add Houseplant

[vinayak-mehta]

Summary

Hey folks, we open-sourced the tool we use at @juneHQ to manage our clickhouse schema. Would love to add it to this list of migration tools in the clickhouse docs.

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/en/integrations/index.mdx

[CLAassistant]

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