Build docker image

[chelmertz]

• build docker image through github action
• update readme's installation instructions
• test drive image locally in favor of systemd service
• expose http via 9876 by default
• pass the sqlite db as a volume
• lint dockerfile with https://github.com/hadolint/hadolint (in a github workflow)

[chelmertz]

https://docs.github.com/en/packages/managing-github-packages-using-github-actions-workflows/publishing-and-installing-a-package-with-github-actions

[chelmertz]

https://hub.docker.com/_/golang

[chelmertz]

https://github.com/nektos/act

[chelmertz]

After this, elly becomes usable at mac, might be time to showcase it more at work.