docs: update README.md to include ports

Update readme.md include both method to expose the container.

Author: otaviosilva22

README.md

@@ -78,7 +78,9 @@ services:
       - NODE_ENV=production
     volumes:
       - ./:/home/node/app
-    ports:
+    expose:
+      - "8081"
+    ports: #use if it is necessary to expose the container to the host machine
       - "8081": "8081"
     command: "npm start"
 ```