link 3 app to firebase code example

Example: deploy to firebase using trivis

// get token in terminal
$ firebase login:ci
$ // token here

// add token to travis  settings

// create file .travis.yaml
language: node_js
node_js: 
  - "12"
script:
  - npm install
  - npm run build
  - echo "Deploying!"
install:
  - npm install -g firebase-tools
after_success:
  - firebase deploy --token $FIREBASE_TOKEN
  
  
$ firebase init

$ git push

// done