Moving to Alpine image + Autobuild

[d3vilh]

Moved to Alpine Linux base image (from Debian) to reduce container image size 10 times:

philipp@d3vpi:~/build/rpi_export $ docker image ls | grep rpi_exporter | grep -E 'alpine|debian'
d3vilh/rpi_exporter-arm64              alpine        aa0aadc1ef01   13 minutes ago   13.9MB
d3vilh/rpi_exporter-arm64              debian        d50133320582   7 weeks ago      129MB
philipp@d3vpi:~/build/rpi_export $

Also I include building of binary inside the container. To build you just need to run:

docker build --force-rm=true -t rpi_exporter-arm64 .

and then test:

docker run --interactive --tty --rm rpi_exporter-arm64

compose file is the same.