Add initial pm docs

source/_components/sensor.particulate_matter.markdown

@@ -0,0 +1,35 @@
+---
+layout: page
+title: "Particulate matter Sensor"
+description: "Instructions how to integrate Particulate matter (PM) sensors within Home Assistant."
+date: 2015-08-09 12:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: mqtt.png
+ha_category: Sensor
+ha_release: 0.26
+ha_iot_class: "Local Push"
+---
+
+
+The `serial_pm` sensor platform allows you to use your Particulate matter (PM) sensors with Home Assistant.
+
+To use your PM sensor in your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yml entry
+sensor:
+  platform: serial_pm
+  serial_device: /dev/tty.SLAB_USBtoUART
+  name: Nova
+  brand: novafitness
+```
+
+Configuration variables:
+
+- **serial_device** (*Required*): The port where the sensor is connected.
+- **name** (*Optional*): The name of the sensor. 
+- **brand** (*Required*): The type or brand of the sensor.
+