Add a section for pre-commit in README.md

[akagami-harsh]

Pull Request Template for Kubeflow Manifests

✏️ Summary of Changes

• added a section for pre-commit in the README
• made some minor improvements in README

📦 Dependencies

🐛 Related Issues

• feat: Add pre-commit hooks for automated code quality checks #3001 (comment)

✅ Contributor Checklist

• I have tested these changes with kustomize. See Installation Prerequisites.
• All commits are signed-off to satisfy the DCO check.

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[juliusvonkohout]

/lgtm
/approve

[google-oss-prow]

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