Add buildx configuration step

Author: guilhem

.github/workflows/docker.yml

@@ -24,6 +24,7 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.CR_PAT }}
 
+      - uses: docker/setup-buildx-action@v1
       - name: Push to GitHub Packages
         uses: docker/build-push-action@v2
         with: