Suggestion for device_class

[nsleigh]

First off, thanks for this code, helped me get my "ESP32-C6: ePulse Feather" battery monitor working.

For the battery voltage I suggest using this conifg to stop it showing up as a battery:

    battery_voltage:
      name: Battery voltage
      id: batt_v
      device_class: voltage
      state_class: measurement

For the rate setting I couldn't really find a suitable class so did this:

    rate:
      name: Battery discharge rate
      id: batt_discharge_rate
      device_class: ""
      state_class: measurement

(I needed this to stop my low battery template finding these two entities and reporting them as low batteries.)