[Feature request]: Use battery_charging device class for charging sensors

[deosrc]

Is your feature request related to a problem? Please describe

I'm creating an automation to alert to any device left charging when leaving the house (fire risk). Ideally I want to have it automatically include any new devices by using a Jinja template similar to the below:

{{ states.binary_sensor | selectattr('attributes.device_class', '==', 'battery_charging') | list }}

Unfortunately it seems the charging sensors from Z2M do not use the device class, or at least not for the devices I have (https://www.zigbee2mqtt.io/devices/ZNJLBL01LM.html#aqara-znjlbl01lm).

Describe the solution you'd like

Battery charging sensors be configured with the battery_charging device class.

Describe alternatives you've considered

Manually setting the device class in Home Assistant, but this would need to be done for every new device added.

Additional context

This would also change the display in HA to read "Charging" and "Not charging" rather than "On" and "Off".