feat: add CI to build and push docker image to Github package

[JinIgarashi]

I added a workflow in CI.yml to build docker image and push it to GitHub package's container registry. I believe having an official docker image is useful for developers to use tilemaker easily.

After merging this pull request, every push to master branch trigger this workflow to update docker image in Github.

You should be able to pull docker image as following command

docker pull ghcr.io/systemed/tilemaker:master

or directly run as follows

docker run -v /Users/Local/Downloads/:/srv -i -t --rm ghcr.io/systemed/tilemaker:master /srv/germany-latest.osm.pbf --output=/srv/germany.mbtiles

You can try docker image through my forked repo's Github Package (https://github.com/JinIgarashi/tilemaker/pkgs/container/tilemaker)

For this PR, nothing needs to be done in the repository settings.

As you are discussing in #365, there are some restriction of use of Github Packages if this repository is private access. But I believe there is no disadvantage of using it since this is public repo and open source project.

[systemed]

This looks great - thank you. I'm very much a Docker neophyte but happy to merge this. Look forward to further feedback as to how well it works.

[leonardehrenfried]

This is a great addition that I was trying to get merged for a while: #365

I will give this a try very soon.

[leonardehrenfried]

I cannot see the repository and I believe you have to make it public as it's private by default. That's what I had to do for another project.

@systemed I think the url to do it is https://github.com/systemed/tilemaker/pkgs/container/tilemaker

[JinIgarashi]

GitHub package is public. You can access freely. Check the following GitHub package page.

https://github.com/systemed/tilemaker/pkgs/container/tilemaker

docker pull ghcr.io/systemed/tilemaker:master is the command to pull Docker image.

[leonardehrenfried]

You're right. I'm blind...