Feedback on /integrate/prometheus: Usage with Prometheus Pushgateway

### Documentation feedback

- Page title: Prometheus
- Page URL: https://cratedb.com/docs/guide/integrate/prometheus/index.html
- Source: https://github.com/crate/cratedb-guide/blob/main/docs/integrate/prometheus/index.md

---

In the same spirit like the [existing usage tutorial](https://cratedb.com/docs/guide/integrate/prometheus/usage.html), but blended with ingredients of others, where you actively "submit data" to the system, we think it is sensible to demonstrate a dedicated use case example looping in the [Prometheus Pushgateway](https://github.com/prometheus/pushgateway).

- https://cratedb.com/docs/guide/integrate/amqp/usage.html#submit-data
- https://cratedb.com/docs/guide/integrate/mqtt/usage.html#submit-data
- https://cratedb.com/docs/guide/integrate/statsd/usage.html#submit-data

```shell
echo "temperature 42.42\nhumidity 83.1" | curl --data-binary @- http://pushgateway.example.org:9091/metrics/job/some_job
```