add Webpack Butternut Plugin (modern minifier)

README.md

@@ -198,6 +198,7 @@ Inspired by the [awesome](https://github.com/sindresorhus/awesome) list. Feel fr
 - [FileManager Webpack Plugin](https://github.com/gregnb/filemanager-webpack-plugin) - Copy, move, delete files and directories before and after Webpack builds -- *Maintainer*: `Gregory Nowakowski` [![Github][githubicon]](https://github.com/gregnb)
 - [Duplicate Package Checker Webpack Plugin](https://github.com/darrenscerri/duplicate-package-checker-webpack-plugin) - Warns you when multiple versions of the same package exist in your bundle -- *Maintainer*: `Darren Scerri` [![Github][githubicon]](https://github.com/darrenscerri)
 - [PurgeCSS Webpack Plugin](https://github.com/FullHuman/purgecss-webpack-plugin) - A plugin to remove unused css with purgecss -- *Maintainer*: `Floriel Fedry` [![Github][githubicon]](https://github.com/Ffloriel)
+- [Webpack Butternut Plugin](https://github.com/MaxGraey/webpack-butternut-plugin) - Webpack plugin for fast, future-friendly minifier with supporting ES2015+. -- *Maintainer*: `Max Graey` [![Github][githubicon]](https://github.com/MaxGraey)
 
 [Back to top](#table-of-contents)