Add device classes new in HA 2021.9 (#2248)

esphome/components/pm1006/sensor.py

@@ -4,6 +4,7 @@ from esphome.components import sensor, uart
 from esphome.const import (
     CONF_ID,
     CONF_PM_2_5,
+    DEVICE_CLASS_PM25,
     STATE_CLASS_MEASUREMENT,
     UNIT_MICROGRAMS_PER_CUBIC_METER,
     ICON_BLUR,
@@ -23,6 +24,7 @@ CONFIG_SCHEMA = cv.All(
                 unit_of_measurement=UNIT_MICROGRAMS_PER_CUBIC_METER,
                 icon=ICON_BLUR,
                 accuracy_decimals=0,
+                device_class=DEVICE_CLASS_PM25,
                 state_class=STATE_CLASS_MEASUREMENT,
             ),
         }