add CDN urls about react-pwa

[tirthbodawala]

@taqimustafa You should not include scripts in head directly rather use loadScript in custom root component. You can have a look at example application with boilerplate.

Also bootstrap is included, even if you are willing to include it from header from other cdn you should use the seo config in src/config/config.js as

// src/config/config.js

{
  // ..other configs
  seo: {
    // ...other seo options
   links: [
     {
       rel: "stylesheet"
       href: "https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css"
     }
   ]
  }
}

But the above method is highly discouraged as it would affect the offline availability of CSS

[taqimustafa]

@tirthbodawala thanks. Will try your solution. 👍