allow provided configuration to be a string

[davidjgoss]

🤔 What's changed?

Allow provided configuration in the options for loadConfiguration to be a argv-style string, as an alternative to a configuration object.

⚡️ What's your motivation?

Many existing framework integrations using the Cli class use an argv string to pass the options in, and also allow end users to express options this way. This will make it easier for such frameworks to adopt the new API, and it uses existing code that we had for handling configuration files anyway.

🏷️ What kind of change is this?

• ⚡ New feature (non-breaking change which adds new 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: 98.383% (+0.004%) from 98.379%
when pulling 3631869 on feat/provided-configuration-string
into 53ccc44 on main.