vuepress firebase authentication

 head: [

    [
      "script",
      {
        src: "https://www.gstatic.com/firebasejs/5.5.6/firebase-app.js"
      }
    ],

    [
      "script",
      {
        src: "https://www.gstatic.com/firebasejs/5.5.6/firebase-auth.js"
      }
    ],

    [
      "script",
      {
        src: "https://www.gstatic.com/firebasejs/5.5.6/firebase-firestore.js"
      }
    ],

    [
      "script",
      {
        src: "https://www.gstatic.com/firebasejs/5.5.6/firebase-functions.js"
      }
    ],

    [
      "script",
      {},
      `var config = {
        apiKey: "apikey",
        authDomain: "app.firebaseapp.com",
        databaseURL: "https://app.firebaseio.com",
        projectId: "appname",
        storageBucket: "appname.appspot.com",
        messagingSenderId: "12345"
      };
      firebase.initializeApp(config);
      const firestore = firebase.firestore();
      const settings = { /* your settings... */
          timestampsInSnapshots: true
      };
      firestore.settings(settings);`
    ],
    ]