add timeline visualisation for parallel runners

We're in the process of removing tight coupling to Gherkin 5 from Cucumber-JVM. Its [TimelineFormatter](https://github.com/cucumber/cucumber-jvm/blob/master/core/src/main/java/io/cucumber/core/plugin/TimelineFormatter.java) is tightly coupled to Gherkin 5, and should be removed.

Moreover, the very useful functionality in `TimelineFormatter` should be available to users of other Cucumber implementations that support parallelism (currently only Cucumber.js).

We already have early stage support for rendering Cucumber in [cucumber-react](), which is wrapped as a standalone command-line tool in [html-formatter](https://github.com/cucumber/cucumber/tree/master/html-formatter). It would make sense to improve `cucumber-react` with the ability to render the same UI as the Cucumber-JVM `TimelineFormatter` (using React).

Also see cucumber/common#755

/cc @charlierudolph @boaty82 @mpkorstanje @vincent-psarga