The code of this plugin is published under MIT License.
So if you are contributing to this plugin / extension, it is important that the source code is distributed under MIT license.
Almost all the heavy-lifing of this plugin (say, interacting with sass library or using sass command line) is done by the common library - DartSass Plugin Common.
So if you are looking for a bug / feature, check the dartsass-plugin-comon repository for the actual code.