0.1: Add compatibility for homeassistant energy dashboard (#5)

* Update Dockerfile to use an alpine image as base

Use python3.8-alpine as base image for a smaller footprint.

* Change `unit_of_measurement` attribute to "kWh" and add other attributes for compatibility with homeassistant enrgy dashboard

Co-authored-by: vluser <user@host.net>

First build

latest

Added very first version