[DOC: PIR Motion Sensors] Fix MQTT topic to publish config for Home Assistant

[Ubiquitine]

I noticed that with the suggested topic in rule2, Home assistant doesn't detect the device/sensor.
After some digging with MQTT explorer I discovered that MQTT integration requires a particular structure of the topic tree under /homeassistant . Sensors configuration should be nested under their type parent-topics, e.g. /homeassistant/sensor/<Sensor ID>, or in that case /homeassistant/binary_sensor/<Sensor ID> .
Also, not included in the PR is additional parameter for the device:

rule2 on system#boot do publish2 homeassistant/binary_sensor/%topic%/config {
  "name": "Motion Sensor",
  "state_topic": "stat/%topic%/MOTION",
  "payload_on": 1,
  "availability_topic": "tele/%topic%/LWT",
  "payload_available": "Online",
  "payload_not_available": "Offline",
  "device_class": "motion",
  "force_update": true,
  "off_delay": 30,
  "unique_id": "%deviceid%_motion",
  "device": {
    "identifiers": [
      "%deviceid%"
    ],
    "name": "WeMos D1 Mini" // Just an example, could be "%deviceid%"
  }
} endon

Without the name added to the device parameters, HA shows the sensor as Connected via Unnamed device