Update readme with build docs

Makefile

@@ -0,0 +1,22 @@
+IMAGE_NAME        = borgbackup
+IMAGE_REPOSITORY ?= vcs.enp.one/skylab
+VERSION          ?= 1.2.3
+
+OCI_CMD = $(shell which podman || which docker)
+
+ifeq ($(OCI_CMD),)
+    $(error "No supported container build tool found (one of: podman, docker)")
+endif
+
+image: ## Build docker container
+	$(info Using $(OCI_CMD) for container interface)
+	@ $(OCI_CMD) build . --file Containerfile --tag $(IMAGE_NAME):$(VERSION) --build-arg borg_version=$(VERSION)
+
+publish: image ## Build docker container and publish to the docker registry
+	@ $(OCI_CMD) tag $(IMAGE_NAME):$(VERSION) $(IMAGE_REPOSITORY)/$(IMAGE_NAME):$(VERSION)
+	@ $(OCI_CMD) push $(IMAGE_REPOSITORY)/$(IMAGE_NAME):$(VERSION)
+
+latest: publish ## Build docker container and publish to the docker registry as the latest version
+	@ $(OCI_CMD) tag $(IMAGE_NAME):$(VERSION) $(IMAGE_NAME):latest
+	@ $(OCI_CMD) tag $(IMAGE_REPOSITORY)/$(IMAGE_NAME):$(VERSION) $(IMAGE_REPOSITORY)/$(IMAGE_NAME):latest
+	@ $(OCI_CMD) push $(IMAGE_REPOSITORY)/$(IMAGE_NAME):latest

README.md

@@ -1,3 +1,5 @@
-# borgmatic
+# borgbackup
 
-Docker container for running Borg backups
+OCI container for running Borg backups
+
+Use `make image` to build the container and `make latest` to publish to VCS