Support configurable NamingStrategy.ExampleName

[mpkorstanje]

🤔 What's changed?

Support configurable NamingStrategy.ExampleName

For example:

public final class MyJUnitXmlFormatter implements ConcurrentEventListener {

    private final MessagesToJunitXmlWriter writer;

    public JUnitFormatter(OutputStream out) {
        this.writer = new MessagesToJunitXmlWriter(NamingStrategy.ExampleName.PICKLE, out);
    }

    @Override
    public void setEventPublisher(EventPublisher publisher) {
        publisher.registerHandlerFor(Envelope.class, this::write);
    }

    private void write(Envelope event) {
        try {
            writer.write(event);
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }

        if (event.getTestRunFinished().isPresent()) {
            try {
                writer.close();
            } catch (IOException e) {
                throw new IllegalStateException(e);
            }
        }
    }

}

Note: Cucumber-JVM at present doesn't allow much configuration of plugins. To take advantage of this new option, the class above must be copied. And can be used in Cucumber-JVM with
cucumber.plugin=com.example.MyJUnitXmlFormatter:target/report.xml.

Fixes: #27

🏷️ 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.