Add support for WebDriver in Standalone Mode

[juenobueno]

WebDriver can be used in Standalone Mode which allowed WebDriver to be used directly, i.e. without the CLI Testrunner. However, I believe using services in Standalone Mode requires the setup and teardown functions of a service to be called manually, as seen in this example by WireMock.

Could I please ask for support to be added to users who use WebDriver in Standalone Mode. I propose that the before setup function takes in a browser argument as it does not exist globally in Standalone Mode. This pattern is actually recommended in the WebDriver docs.

// index.js

...

  before(config, capabilities, browser) {
    ...
  }
...