Use GitHub Actions to build Docker images

[stevehipwell]

Using a GitHub Action workflow to build the Docker images should give more control and visibility on how the images are created. It will also allow both #313 and #314 to be implemented.

I'd suggest basing the workflow on calyptia-fluentd-docker-image but with an additional step/job to promote the tag to a GH release for tracking.

[patrick-stephens]

Seems reasonable to me, although I'd probably try to use the metadata action with Github and just push all images regardless to GHCR.io apart from possibly PRs as they'll need extra permissions on forks.
https://github.com/fluent/fluent-bit/blob/master/.github/workflows/call-build-images.yaml#L69

[ashie]

Another issue for Windows: #276