Added publish build step

Makefile

@@ -2,8 +2,13 @@
 #
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-BUILDER := docker buildx
+DOCKER := docker
+BUILDER := ${DOCKER} buildx
 TAG := git.schmidl.dev/schtobia/buildimage
 
 build: dockerfile
 	@${BUILDER} build --build-arg=GIT_COMMIT=$(shell git describe --always) --build-arg=VERSION=$(shell git describe --tags --always --dirty) --build-arg=TIMESTAMP="$(shell date -u -Iseconds)" -t ${TAG} .
+
+.PHONY: publish
+publish: build
+	@${DOCKER} push ${TAG}