use mapping for namespaces rather than list (#34) #60

Job	Run time
build-container (amd64, ubuntu-latest)	35s
build-container (arm64, ubuntu-24.04-arm)	36s
push-multiarch-manifest (quay.io/validatedpatterns, false)	36s
push-multiarch-manifest (quay.io/hybridcloudpatterns, true)	1m 4s
	2m 51s

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