Are you here from the Scaffold lesson in SignalR Mastery? This is the command I used!
npm install -D -E clean-webpack-plugin@3.0.0 css-loader@3.4.0 html-webpack-plugin@3.2.0 mini-css-extract-plugin@0.9.0 ts-loader@6.2.1 typescript@3.7.5 webpack@4.41.5 webpack-cli@3.3.10