This guide will let you through the process of migrating your Rails Application from Sprockets to Webpacker 3.0. Even though Webpacker suggests to keep using Sprockets for css and images, I don’t really see why we should keep two bundlers at the same time when we can simply use only Webpacker.

https://medium.com/@coorasse/goodbye-sprockets-welcome-webpacker-3-0-ff877fb8fa79