First stable version of Config package was tagged.
This Composer plugin provides assembling of configurations distributed with composer packages. It allows putting configuration needed to use a package right inside thus implementing a plugin system. The package becomes a plugin holding both the code and its configuration.
The package, despite its primary goal of being used in Yii3, is very flexible and allows to build various plugin systems. The config assembly plan is prepared on installing dependencies but the build itself if done runtime in an efficient manner simplifying debugging and development a lot. What is written in config files is what actually being executed so configuration errors displayed are helpful.
You can find more details and a usage guide in the package readme.
As usual, the package is covered with tests, has high mutation score and is checked with Psalm.