Please how can i add another collection in my config file example (db, 'posts', 'comments')

Question

This codes below is a configuration file in my vue application, Please how can i add another collection in my config file example (db, 'posts', 'comments')

import { initializeApp } from "firebase/app";
import {getFirestore, collection} from 'firebase/firestore'
import { getAuth } from "firebase/auth";

const firebaseConfig = {
  apiKey: "",
  authDomain: "",
  projectId: "",
  storageBucket: "",
  messagingSenderId: "",
  appId: ""
};

const app = initializeApp(firebaseConfig);
const db = getFirestore(app);
const auth = getAuth(app);

const postColRef = collection(db, 'posts');

export { auth };
export default  postColRef;