sdk, core: add Charger interface

[bjia56]

Tested using the following script:

class TestCharger implements OnOff {

    async turnOff(): Promise<void> {
        try {
            device.chargeState = "trickle";
            //device.chargeState = "not-charging";
        } catch (e) {
            device.console.log(e);
        }
        device.on = false;
        device.console.log(device.chargeState);
    }

    async turnOn() {
        try {
            device.chargeState = "charging";
        } catch (e) {
            device.console.log(e);
        }
        device.on = true;
        device.console.log(device.chargeState);
    }
}

device.handleTypes(ScryptedInterface.Charger);

export default TestCharger;