Summary

Adds Vale to docs CI, and for running locally.

Workflow description:

• A user opens a PR.
• The workflow checks which lines were changed in which files.
• Vale is run for those files.
• If Vale picks up issues which are suggestions or warnings it posts them as an annotation on the file in the "Files changed" tab.
• If Vale has any errors it will fail. (We can choose which rules will error vs just warn)

We can run locally using yarn check-prose (also called as part of check-style). By default it checks only those files which are modified on your branch. If you want to check specific files use yarn check-prose -f 'docs/best-practices/json_type.md'

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