feat(workflow): add digest-bearing image publication workflows #45

Job	Run time
sailr-workflow (ci)	2m 48s
sailr-workflow (ci-build-plan)	2m 22s
sailr-workflow (ci-build-push-plan)	2m 13s
sailr-workflow (ci-deploy-plan)	2m 51s
sailr-workflow (ci-generate)	2m 38s
sailr-ci-build	0s
staging-deploy	0s
	12m 52s

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