Feature request: add hw / sw version in MQTT payload

[jasperslits]

This is a feature request.

If the sw version is sent via the MQTT payload, it is possible to leverage the Home Assistant Update notifier to create a new notification in Home Assistant alerting the user that there's a new release available.

The content of https://raw.githubusercontent.com/arjenhiemstra/ithowifi/master/compiled_firmware_files/firmware.json can already be parsed but it's unknown which sw version runs on the device.

@benjamin-dcs and I have built an integration to create sensors as you know and this seems a nice to have. The assumption that people check Home assistant more often than the Addon itself and I guess few people use Github notifications or Tweakers notifications.

Obviously low priority and I understand there are higher priority items to work on.