support YAML for config files

[davidjgoss]

🤔 What's changed?

Add support for YAML as a configuration file format.

⚡️ What's your motivation?

We support JS and JSON; YAML is the obvious missing option.

🏷️ What kind of change is this?

• ⚡ New feature (non-breaking change which adds new behaviour)

♻️ Anything particular you want feedback on?

Also as part of this, JSON configuration files are loaded with fs.readFile rather than require - this is a small non-breaking step towards moving away from require for everything.

📋 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 increased (+0.006%) to 98.335% when pulling 111e376 on feat/config-yaml into 79ba4bd on main.