Add blog and update number and sensor entity docs

blog/2024-12-04-area-squared-units.md

@@ -0,0 +1,15 @@
+---
+author: mikey0000
+authorURL: https://github.com/mikey0000
+title: "New area device class"
+---
+
+### Summary of changes
+A new `AREA` device class is now available for number and sensor entities, together with automatic unit conversion based on the unit system.
+A corresponding `UnitOfArea` unit enumerator, and `AreaConverter` converter class have been added to support the new device class.
+
+### Backward compatibility
+The `AREA_SQUARE_METERS` constant has been deprecated and will be removed in Home Assistant `2025.12`.
+Custom integrations should be adjusted to use `UnitOfArea.SQUARE_METERS`.
+
+More details can be found in the [Number documentation](/docs/core/entity/number#available-device-classes) and [Sensor documentation](/docs/core/entity/sensor#available-device-classes)

docs/core/entity/number.md

@@ -33,6 +33,7 @@ If specifying a device class, your number entity will need to also return the co
 | ---- | ---- | -----------
 | `NumberDeviceClass.APPARANT_POWER` | VA | Apparent power |
 | `NumberDeviceClass.AQI` | None | Air Quality Index
+| `NumberDeviceClass.AREA` | m², cm², km², mm², in², ft², yd², mi², ac, ha | Area                                                                                                                                                                                                                                  |
 | `NumberDeviceClass.ATMOSPHERIC_PRESSURE` | cbar, bar, hPa, inHg, kPa, mbar, Pa, psi | Atmospheric pressure, statistics will be stored in Pa.
 | `NumberDeviceClass.BATTERY` | % | Percentage of battery that is left
 | `NumberDeviceClass.BLOOD_GLUCOSE_CONCENTRATION` | mg/dL, mmol/L | Blood glucose concentration```

docs/core/entity/sensor.md

@@ -34,7 +34,8 @@ If specifying a device class, your sensor entity will need to also return the co
 | ---- | ---- | -----------
 | `SensorDeviceClass.APPARENT_POWER` | VA | Apparent power
 | `SensorDeviceClass.AQI` | None | Air Quality Index
-| `SensorDeviceClass.ATMOSPHERIC_PRESSURE` | cbar, bar, hPa, mmHG, inHg, kPa, mbar, Pa, psi | Atmospheric pressure.
+| `SensorDeviceClass.AREA` | m², cm², km², mm², in², ft², yd², mi², ac, ha | Area
+| `SensorDeviceClass.ATMOSPHERIC_PRESSURE` | cbar, bar, hPa, mmHG, inHg, kPa, mbar, Pa, psi | Atmospheric pressure
 | `SensorDeviceClass.BATTERY` | % | Percentage of battery that is left
 | `SensorDeviceClass.BLOOD_GLUCOSE_CONCENTRATION` | mg/dL, mmol/L | Blood glucose concentration```
 | `SensorDeviceClass.CO2` | ppm | Concentration of carbon dioxide.