Support aarch64 by default

[elibroftw]

When I follow the template-starter, using a custom Dockerfile results in only amd64 images pushed (and thus available to pull) to ghcr.io.

Ideally the devcontainer CLI would handle setting up QEMU and handling the multi-action, otherwise I have to resort to what home-assistant is doing, https://github.com/home-assistant/devcontainer/blob/c1479dcf6b8b55e2cdfaba53515fe547d5acd08a/.github/workflows/builder.yaml#L50, which is to not use the devcontainer-cli at all.

See devcontainers/template-starter#46

[elibroftw]

If you add platforms as an input then there is no problem. I have a custom build script. See my devcontainer repo