Make air quality level configurable?
Hi. I know I'm a bit annoying but I've another question. Or better: This time a feature request.

In the `AirPurifierAccessory.js` is the following part
```
if (pm25Density <= 7) {
return Characteristic.AirQuality.EXCELLENT;
} else if (pm25Density > 7 && pm25Density <= 15) {
return Characteristic.AirQuality.GOOD;
} else if (pm25Density > 15 && pm25Density <= 30) {
return Characteristic.AirQuality.FAIR;
} else if (pm25Density > 30 && pm25Density <= 55) {
return Characteristic.AirQuality.INFERIOR;
} else if (pm25Density > 55) {
return Characteristic.AirQuality.POOR;
}
```

I understand these values are based on some research, but I'd love to configure this, so I could finetune my automations a bit more. Other plugins that don't work with my air purifier had a simple array for this, where one could simply add five values for this.

Would it be possible to add this to your plugin?