use react-components 20.0.0, update docs

[davidjgoss]

🤔 What's changed?

• Use latest React components including with new package name
• Update documentation accordingly
• Add a readme to the javascript package that explains to users that it's internal (I have seen a few users in the wild installing it themselves)

🏷️ What kind of change is this?

• 🐛 Bug fix (non-breaking change which fixes a defect)
• ⚡ 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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[aurelien-reeves]

Looks good

Just have to fix the CI

Also, could be nice to have the same notice in READMEs for ruby and java implementations

[aurelien-reeves]

👍