Text changes needed to address Webpack and Babel installations

[jasonflorack]

I propose making some changes to the installation instructions in Chapter 6 to set up Webpack and Babel. At the end of the chapter, when typing npm start as instructed by the author, I came across two issues. Here are the issues and how I solved them:

1. Important part of error message: The CLI moved into a separate package: webpack-cli To resolve, at the command line, I typed npm install --save-dev webpack-cli -D and re-ran npm start.

2. Important part of error message: babel-loader@8 requires Babel 7.x (the package '@babel/core') To resolve, at the command line, I typed npm install --save-dev babel-loader@^7.0.0 and re-ran npm start.

The third time was the charm, and npm start worked as expected.