How to include static file folder in Electron Forge when build the application?

I'm trying to use Electron Forge to build an app using the TypeScript + Webpack template. Since I need to change the app icon, I've created an asset/icon folder in the root directory to store my icons. This works perfectly while developing. But after I run the make command and try to run the app, it's saying can't find the icon and I see the asset was not included in the output. So my question is how can I include my static folder into the webpack during build process?