https://github.com/tcoopman/image-webpack-loader exists. The plugin will recompress png, jpeg, and svg images, as well as optionally converting the first two to webp. That said, it seems to have a persistent bug where jpegs are always converted to webp while retaining their original extention, and the maintainer doesn't seem to have the time to fix it or merge pull requests. If you wanted to help them out with that, they'd likely be amenable.

Something that I've not seen is a plugin/loader that will automatically use the <picture> tag to make available multiple auto-generated source images and a fallback <img>. It'd be great to be able to

import myImage from 'res/img/my_img.png'

and have myImage be a string like

<picture><source srcset="[generated-name-of-my-image.webp]"><img src="generated-name-of-my-image.png"]></picture>