[docs] Deploy previews are broken due to baseUrl-issues

Created by: petetnt

After changing the baseUrl to / in https://github.com/facebook/create-react-app/pull/7499 the Netlify still deploys to *.netlify.com/create-react-app which causes all the assets to 404.

See for example https://deploy-preview-7521--create-react-app.netlify.com/create-react-app/

cc @iansu