Edit Vercel config so all merges into `main` prompt a site build and deploy.

[justindeguzman]

Currently, commits merged to main are only deployed to Vercel if merged by a member of the ClickHouse Vercel organization with the role of Developer or higher.

All commits to main should trigger a deploy to make contributing to the docs easier.

From the Vercel support team:

Thank you for your patience. You can create a custom workflow using GitHub Action or CI tool and use Vercel CLI to deploy production deployment from Main. This will ensure it triggers deployment regardless of the role of the user: https://vercel.com/guides/how-can-i-use-github-actions-with-vercel