correct docker compose for building on GH Actions

sut:

  build: .

  command: echo "build complete"

version: '3'

services:

  web:

    container_name: webapp-frontend

  universc:

    container_name: universc

    build: .

    ports:

      - "5000:5000"

  redis:

    container_name: redis-backend

    image: "redis:alpine"

    command: echo "build complete"