Thank you, I can see the files now.
Regarding the above error you see, it will likely go away, if you remove this line: https://github.com/nimeshakya/react-practice/blob/82e8104276bb820c772e71c9480c7dca327e092a/public/index.html#L17
However, I believe the error is related to the build package (which is not pushed to GitHub, and should not be pushed). That is, when CRA builds your app (when viewing), it should create a manifest. The error sounds like something has gone wrong with the build.
Also, I notice you do not import React in App.js react-practice/App.js at main · nimeshakya/react-practice (github.com)
Try adding this at the top of the above mentioned file:
import React from 'react';
Hope this helps