This is an extension that uses https://webpack.js.org to bundle and minify its sources. Using webpack will help to reduce the install- and startup-time of large extensions because instead of hundreds of files, a single file is produced.
Webpack is configured in the webpack.config.js-file. Find annotation inside the file itself or refer to the excellent webpack documentation: https://webpack.js.org/configuration/. In short, the config-files defines the entry point of the extension, to use TypeScript, to produce a commonjs-module, and what modules not to bundle.
The scripts-section of the package.json-file has entries for webpack. Those compile TypeScript and produce the bundle as well as producing a minified production build. Note, that there is no dedicated TypeScript-script as webpack takes care of that.