Update '.woodpecker/.build.yml'

.woodpecker/.build.yml

@@ -2,6 +2,8 @@ pipeline:
     build_and_publish:
         image: woodpeckerci/plugin-docker-buildx
         secrets: [ DOCKERHUB_USER ]
+        environment:
+            DOCKERHUB_USER=${DOCKERHUB_USER}
         settings:
             username: ${DOCKERHUB_USER}
             password: ${DOCKERHUB_TOKEN}