Use correct favicon

[davidjgoss]

🤔 What's changed?

Change the embedded SVG favicon for the HTML file to be the correct (non-SmartBear) Cucumber mark.

Also, tweak the acceptance test in the javascript package so each example is output to a file for easy inspection.

🏷️ What kind of change is this?

• 🐛 Bug fix (non-breaking change which fixes a defect)

📋 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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[luke-hill]

For simplicity can we see a before / after. But the code seems fine from my end