feat: Add the possibility to set examples to the default handler behvior

[bubu11e]

When trying to add examples for the default tonic status with the function fizz.Response like this:

routerGroup.POST(
            "", []fizz.OperationOption{
                fizz.Summary("My Summary"),
                fizz.ResponseWithExamples(
                    fmt.Sprintf("%d", http.StatusAccepted),
                    "toto", nil, nil, map[string]string{
                        "example ": "example",
                    }),
            },
            tonic.Handler(<the_handler>, http.StatusAccepted),
        )

we get the following error:

panic: error while generating OpenAPI spec on operation XXXX : response with code XXX already exists [recovered,repanicked]

This request add the possibility to set multiples examples for the default handler behavior.