jsbundling-railsのCSSプロセッサ版です。 jsbundling-railsのissueでJavaScriptバンドラー以外をサポートしないのか聞かれてDHHは次のように答えました。
https://github.com/rails/jsbundling-rails/issues/4#issuecomment-914039291
Although given how little code there actually is in this gem, we may also just consider putting it in a sister gem (like I originally had with esbuild-css and rollupjs-rails). Perhaps cssbundling-rails? Then we could have installers for Dart Sass, TW, plain PostCSS?
9時間後に...
https://github.com/rails/jsbundling-rails/issues/4#issuecomment-914393113
It's happening: https://github.com/rails/cssbundling-rails
できちゃった