Publish image on tag

As we are pretty much committed to github actions, we should
probably rely on it to push the images on tag.

This covers the missing bits.

.github/workflows/on-tag.yaml

@@ -24,7 +24,17 @@ jobs:
           go-version: "${{ steps.awk_gomod.outputs.version }}"
       - run: |
           make DH_ORG="${{ github.repository_owner }}" VERSION="${GITHUB_REF#refs/tags/}" image
+
       - uses: Azure/container-scan@v0
         with:
           image-name: docker.io/${{ github.repository_owner }}/kured:${GITHUB_REF#refs/tags/}
-      # We should add a step to publish the image on tag.
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Publish image
+        run: |
+          make DH_ORG="${{ github.repository_owner }}" VERSION="${GITHUB_REF#refs/tags/}" publish-image