Name the buildx step

This allows easy access to the step output variables.

.github/workflows/ci.yaml

@@ -37,6 +37,7 @@ jobs:
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
       - name: Set up Docker Buildx
+        id: buildx
         uses: docker/setup-buildx-action@v3
       - name: Log into GitHub Container Registry
         run: echo "${{ secrets.REGISTRY_ACCESS_TOKEN }}" | docker login https://ghcr.io -u ${{ github.actor }} --password-stdin