Setting base href using Environment variables

This problem was solved. Follow these steps:

1. In package.json Set homepage key to ""
2. In .env.staging file Set PUBLIC_URL=/survey
3. No need to use <base href>. Can be removed from HTML file

4. Change links for stylesheet to

   <link rel="stylesheet" href="%PUBLIC_URL%/vendor/bootstrap/css/bootstrap.min.css">

No need to add process.env