message: add login note on angular pwa guide
diff: @@ -74,6 +74,8 @@ Next, in a Terminal, install the Firebase CLI:
  $ npm install -g firebase-tools
  ```
  +> Note: If it's the first time you use firebase-tools, login to your Google account with `firebase login` command.
  +
  With the Firebase CLI installed, run `firebase init` within your Ionic project. The CLI prompts:
  **"Which Firebase CLI features do you want to set up for this folder?"** Choose "Hosting: Configure and deploy Firebase Hosting sites."
  