Typos in the Readme and App.js file

The app.js file has an outdated comment: "// All this properties are set on auth0-variables.js". Those properties are currently set on a .env file. 

The readme.md file doesn't explain that for the seed project to work on Windows the .env file (in the case that it has to be created by the user) needs to have a newline in the end, after the URL. 
