improving docker build

.github/workflows/python-publish.yml

@@ -32,6 +32,7 @@ jobs:
         run: for i in {1..100}; do python -m pip install 'nicegui==${{ steps.get_version.outputs.VERSION }}' && break || sleep 2; done
 
   docker:
+    needs: pypi
     runs-on: ubuntu-latest
 
     steps:
@@ -69,10 +70,14 @@ jobs:
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@master
+        with:
+          install: true
       - name: Build
         uses: docker/build-push-action@v2
         with:
-          builder: ${{ steps.buildx.outputs.name }}
           context: .
           file: ./release.dockerfile
           platforms: linux/amd64,linux/arm64,linux/arm32v5,linux/arm32v6,linux/arm32v7,linux/ppc64le