feat: add pre-commit hook integration

[Tyagiquamar]

Problem

Users wanting to run poutine automatically before committing workflow changes cannot easily integrate it via pre-commit or prek without a dedicated hook manifest.

Solution

• Add .pre-commit-hooks.yaml\ defining the \poutine\ hook entrypoint targeting CI/CD workflow YAML files.
• Update \README.md\ with instructions on how to configure poutine in .pre-commit-config.yaml.

Fixes #454

Validation

• Tested hook configuration and schema.
• Verified test suite passes via Docker (\golang:latest).