Adding a github workflow to automate arm docker builds

[jimmycleuren]

This PR will automate arm docker image build through github actions.

• Go to https://hub.docker.com/settings/security

• New access token

• Give it a name and copy the token

• Go to https://github.com/jgeusebroek/docker-spotweb/settings/secrets/actions

• New repository secret

• Name: DOCKER_USERNAME

• Value: your dockerhub username

• New repository secret

• Name: DOCKER_PASSWORD

• Value: the token you just created on docker hub

You can disable auto building on docker hub after this PR is merged.

[jimmycleuren]

Fixes #26

[jgeusebroek]

Thanks Jimmy! I will look into this asap. I just wanted to let you know I've seen it.

[jgeusebroek]

Thanks, merged!