fix: ensure buildx is available during the release process

Without this, we cannot build the docker image during a release.

.github/workflows/release.yml

@@ -33,6 +33,21 @@ jobs:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Inspect builder
+        run: |
+          echo "Name:      ${{ steps.buildx.outputs.name }}"
+          echo "Endpoint:  ${{ steps.buildx.outputs.endpoint }}"
+          echo "Status:    ${{ steps.buildx.outputs.status }}"
+          echo "Flags:     ${{ steps.buildx.outputs.flags }}"
+          echo "Platforms: ${{ steps.buildx.outputs.platforms }}"
+
       - name: install package_cloud
         run: gem install package_cloud