Provide RestClient example in HTTP Interface Exception Handling section of reference docs

[ciscoo]

Affects: 6.1.1

In the exception handling section, I had expected to see an example using the newly added RestClient:

RestClient restClient = RestClient.builder()
    .defaultStatusHandler(HttpStatusCode::isError, (req, res) -> ...)
    .build();

Or maybe even a small callout that the same setup/arrangement exists for RestClient.

The introduction section before it gives example for each client as well:

[OlgaMaciaszek]

Will get it done.