fix: add id to build step for attestation digest

Author: boxpositron

.github/workflows/docker-publish.yml

@@ -45,6 +45,7 @@ jobs:
             type=raw,value=latest,enable={{is_default_branch}}
 
       - name: Build and push Docker image
+        id: build
         uses: docker/build-push-action@v5
         with:
           context: .