Request: add request latency/duration to --enrich output

[cj]

this is the only feature that I miss from GUI clients like Kreya, Wombat, BloomRPC, etc.

example:

> call --enrich ...

{
    .....
}

code: OK
number: 0
message: ""
duration: 12.34ms

alternatively, this could have its own option, e.g. -d, --duration

[ktr]

Thanks for your suggestion.
It makes sense to add request duration to the output result.

And I think it's better to add the duration to --enrich output.