fix: Unable to control BB-V2-0 thermostats (#139)

This change was identified while investigating why my BB-V2-0 Mysa would
not respond to device state commands from Home Assistant (using
mysq2mqtt). The id type was previously in unix time (seconds), but
should be in milliseconds per the reference here:
https://github.com/dlenski/mysotherm/blob/main/mysa_messages.md Making
this update corrected the behavior and commands now work successfully.

src/api/MysaApiClient.ts

@@ -374,7 +374,7 @@ export class MysaApiClient {
     this._logger.debug(`Sending request to set device state for '${deviceId}'...`);
     const payload = serializeMqttPayload<ChangeDeviceState>({
       msg: InMessageType.CHANGE_DEVICE_STATE,
-      id: now.unix(),
+      id: now.valueOf(),
       time: now.unix(),
       ver: '1.0',
       src: {