There are not many examples of how to use a Webpack 4 on the front-end part of the ASP.NET Core 3.1 MVC application. One way is to use some specific middleware, but here I will use tools and pipelines that are conventional among the front-end developers:
NPM package manager to manage Node.js packages and to run scripts.
SASS to process styles.
Webpack 4 to bundle all things together.
and Visual Studio Code as an IDE.