### Feature and motivation

Be able to link custom OpenTelemetry tracing with the default Selenium grid tracing. See for e.g. https://github.com/llatinov/selenium-observability-java/blob/324b500316be34f5f1426720353d0c4e2e8b5a89/selenium-tests/src/main/java/com/automationrhapsody/observability/TracingWebDriver.java#L81 
It will be useful if I am able to pass my Span as a parent span of Selenium's RemoteWebDriver tracing, so I can trace my actions with corresponding grid actions.

### Usage example

Implement a custom tracing that monitors the tests. It will be of great help to be able to make the default server/grid tracing a child of the custom tracking. In this case, users can monitor how a click of a button in their tests links to grid performance.
ExecutorService executors = Executors.newCachedThreadPool();
    handler.addHandler(Route.get("/status").to(() -> req -> {
      try (Span span = HttpTracing.newSpanAsChildOf(tracer, req, "status")) {
        executors.submit(span.wrap(() -> new HashSet<>(Arrays.asList("cheese", "peas")))).get();
        CompletableFuture<String> toReturn = new CompletableFuture<>();
        executors.submit(() -> {
          try {
            HttpRequest cheeseReq = new HttpRequest(GET, "/cheeses");
            HttpTracing.inject(tracer, span, cheeseReq);
            handler.execute(cheeseReq);
            toReturn.complete("nom, nom, nom");
          } catch (RuntimeException e) {
            toReturn.completeExceptionally(e);
          }
        });
        toReturn.get();
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
      return new HttpResponse();
    }));
    handler.addHandler(Route.get("/cheeses").to(() -> req -> new HttpResponse()));
    Routable routable = handler.with(delegate -> req -> {
      try (Span span = newSpanAsChildOf(tracer, req, "httpclient.execute")) {
        return delegate.execute(req);
      }
    });
    routable.execute(new HttpRequest(GET, "/"));
  }
  private Tracer createTracer(List<SpanData> exportTo) {