Add support for ARM64 architecture in Docker build and push action

[niklhut]

This PR updates the Docker build and push action to include the linux/arm64 platform in addition to linux/amd64. Previously, the build configuration only targeted amd64, which made it impossible to pull the image on Macs with ARM architecture chips.

With this change, the Docker images will be built for both amd64 and arm64 architectures, ensuring compatibility across a wider range of devices, including ARM-based Macs.

[Rdeisenroth]

Hmm seems like Github thinks for some reason the image is too big like this :/

[niklhut]

Well, the failure seems to be because the image could not be uploaded to ghcr.io:

ERROR: failed to solve: failed to push ghcr.io/tudalgo/algotex:pr-67: unexpected status from POST request to https://ghcr.io/v2/tudalgo/algotex/blobs/uploads/: 403 Forbidden

According to this page https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token this is because PRs from forks can only get a read permission for packages, so an upload fails.