workflows: push docker image on release

.github/workflows/ci-build.yml

@@ -33,4 +33,4 @@ jobs:
     - name: build
       uses: docker/build-push-action@v2
       with:
-        file: facilitator/Dockerfile
+        file: ./facilitator/Dockerfile

.github/workflows/push-docker-image.yml

@@ -0,0 +1,27 @@
+name: push-docker-image
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Get the version
+      id: get_version
+      run: echo ::set-output name=VERSION::${GITHUB_REF/refs\/tags\//}
+    - name: Set up Docker build
+      uses: docker/setup-buildx-action@v1
+    - name: Login to DockerHub
+      uses: docker/login-action@v1
+      with:
+        username: isrgautomaton
+        password: ${{ secrets.ISRG_AUTOMATON_DOCKERHUB_AUTH_TOKEN }}
+    - name: build
+      uses: docker/build-push-action@v2
+      with:
+        file: ./facilitator/Dockerfile
+        push: true
+        tags: letsencrypt/prio-facilitator:${{ steps.get_version.outputs.VERSION }}