chore: add CODEOWNERS

[davidjgoss]

🤔 What's changed?

Add CODEOWNERS file that declares people on the build team must be involved in any changes under .github/.

Commonly this file is in the root, but it's supported in here as well and this way the file itself is included in the restrictions.

⚡️ What's your motivation?

As discussed in a recent call, we want to minimise security exposure around release workflows being changed by any committers.

Next step is to see if we can tie this up with branch protection as is hinted at in the docs:
https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners#codeowners-and-branch-protection

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, documentation etc. without changing behaviour)

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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[coveralls]

Coverage remained the same at 98.232% when pulling 4024db3 on codeowners-pocs into a76ee83 on main.