Task: auto-deploy Docker images of master and tags for arm64 arch as well

[erikmd]

Related user(s):

@erikmd, @CJs0800

Related issue(s) or PR(s):

No response

Related project scope(s):

build

The problem:

• https://hub.docker.com/r/ocamlsf/learn-ocaml/tags only deals with linux/amd64, while some linux/arm64/v8 support would be nice

Wanted solution:

Update the two GitHub Actions workflows:

• https://github.com/ocaml-sf/learn-ocaml/blob/master/.github/workflows/deploy-master.yml
• then https://github.com/ocaml-sf/learn-ocaml/blob/master/.github/workflows/release.yml#L91

Using:

• https://github.com/docker/build-push-action#readme
• https://github.com/docker/setup-buildx-action#readme
• https://docs.docker.com/reference/cli/docker/buildx/create/#platform

Note: the version of the build-push-action should also be bumped: https://github.com/ocaml-sf/learn-ocaml/blob/87c7b7fe2698620213eeb5392a96f0f6c974c9af/.github/workflows/deploy-master.yml#L36 to @v6 (in a first, separated commit)

Considered alternatives:

No response

Additional context:

No response