Moved index.css to containers folder

[a-singh09]

Hello everyone, this is my first contribution. I have moved index.css to containers folder but could not move index.js as 'yarn start' could not find index.js in src folder. Maybe command 'react-scripts start' is designed in such way. Is there any way that 'react-scripts start' command check for index.js in src/containers folder.

Here is a screenshot for reference.