Support multi-arch builds

[Sencudra]

Allowing deploy job to build multi-arch builds.

Full Description: https://forum.exercism.org/t/why-its-needed-to-build-docker-image-before-push/19926

[github-actions]

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[ErikSchierboom]

@exercism/maintainers-admin This PR has been tested, but if any track tooling starts behaving weirdly, please let me know.. See https://forum.exercism.org/t/is-load-true-required-for-docker-build-push-image-build-step/19926 for more information