Adding a new feature to GreenLight is always welcome when the feature itself is considered to be useful for other projects as well. While developing something new, it is recommended to keep the following in mind:
Since DevKit is a wrapper Laravel instance to make sure you can test functionality, most of your code changes are going to be applied to the GreenLight repository and not the DevKit one. It is highly recommended to use an IDE that can handle opening subprojects in the same view, like PHPStorm and its "Attach Project" method. This way it is easy to maintain two Git repositories at the same time while still having the advantages of auto-complete and other various helper functions that you would need while developing.
Adding new functionality to GreenLight should be similar to this: