Improve workflow documentation

build-and-push.sh

@@ -44,6 +44,11 @@ else
   docker buildx use "$BUILDER"
 fi
 
+if [[ -n "${REGISTRY_HOST:-}" && -n "${REGISTRY_USER:-}" && -n "${REGISTRY_TOKEN:-}" ]]; then
+  echo "Logging in to $REGISTRY_HOST for non-interactive push"
+  echo "$REGISTRY_TOKEN" | docker login "$REGISTRY_HOST" --username "$REGISTRY_USER" --password-stdin
+fi
+
 echo "Building multi-arch image for $SPYDER_IMAGE on platforms: $PLATFORMS"
 
 docker buildx build \