Add dockerfile

[Yuni-sa]

This commit adds a Dockerfile and .dockerignore to for containerizing the kor CLI tool. #64 #69

example for using the image: docker run --rm -i -v "$KUBECONFIG:/root/.kube/config" kor-image:tag all -n namespace
or instead: docker run --rm -i -v "/path/to/kube/config:/root/.kube/config" kor-image:tag all -n namespace

The image should be pushed to dockerhub and ghcr.io with every release using goreleaser.

I was also thinking about adding to the Dockerfile ENV KUBECONFIG=/kubeconfig making it a bit easier to use the volume: docker run --rm -i -v "/path/to/kube/config:/kubeconfig" kor-image:tag but for now users can just add -e KUBECONFIG=/kubeconfig -v "/path/to/kube/config:/kubeconfig".

@yonahd let me know what you think.

[Yuni-sa]

also instructions should be added to readme.md once the image is pushed.

[yonahd]

The if the kubeconfig is mounted it can be passed with the -k flag. So no need to set the env variable.

The MR looks good. I'll add the docker to the release once I create the registry and add credentials