Automate docker push

.github/workflows/docker.yml

@@ -0,0 +1,26 @@
+name: Docker stuff
+# uses https://github.com/docker/build-push-action
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  docker:
+    # this should prevent the job from running on PRs and should help keep the keys secret
+    if: github.ref == 'refs/heads/main'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Docker Build and Docker Push
+        id: docker_build
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          # According to https://docs.github.com/en/actions/reference/events-that-trigger-workflows#release `$GITHUB_REF` is going to be the tag of the release
+          tags: singlespa/import-map-deployer:${{GITHUB_REF}},singlespa/import-map-deployer:latest