Push docker manifest in CI for multi arch image

ci/steps/build-docker-image.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+main() {
+  cd "$(dirname "$0")/../.."
+  source ./ci/lib.sh
+
+  ./ci/release-container/build.sh
+
+  mkdir -p release-images
+  docker save "codercom/code-server-$ARCH:$VERSION" > "release-images/code-server-$ARCH:$VERSION.tar"
+}
+
+main "$@"