Make sure you download all the items shown in the package.json file

Add the following dev dependencies:

css-loader
file-loader
html-loader
html-webpack-plugin
mini-css-extract-plugin
sass-loader
style-loader
webpack
webpack-cli
webpack-merge

Add the following plugins

optimize-css-assets-webpack-plugin
clean-webpack-plugin

Add the following as a dependency

clean-webpack-plugin