Docker image

[andrewthetechie]

I'm using complexity to build a few static sites and have been using it in my CI pipelines. To use it, I needed it in a docker container.

I setup https://github.com/andrewthetechie/complexity-docker to build those images. Right now I'm building images for 3.8, 3.9, and 3.10 versions of python both on alpine and slim images.

If you're interested in a PR, I'd be happy to PR these changes back to this project to have github actions build images right from here.