ci: build multi-arch Docker images from Release binaries (kubeowler +… #11

Job	Run time
build (aarch64-unknown-linux-musl, ubuntu-latest, aarch64-linux)	4m 19s
build (x86_64-unknown-linux-musl, ubuntu-latest, x86_64-linux)	1m 54s
release	7s
docker	1m 55s
build (x86_64-unknown-linux-musl, ubuntu-latest, x86_64-linux)	1m 54s
docker	1m 56s
release	7s
build (aarch64-unknown-linux-musl, ubuntu-latest, aarch64-linux)	4m 19s
	16m 31s

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