MQTT Broker documentation Suggestions

### Description

I'm following the install instructions for the MQTT Broker [here](https://flowfuse.com/docs/install/local/#docker-install)

### Confusions:
1. Step 2 says _"A default `mosquitto.conf` file can be found in the `broker` directory."_. It is not clear where that `broker` directory is though? How do I find it having pulled the Docker image?
2. The instructions finish after the Docker `run`, but in fact, this does not finish the setup. Instead, we also need to modify our `flowforge.yml`. A reference/link should be made to https://flowfuse.com/docs/install/configuration/#mqtt-broker-configuration-1