How to add original files in the Project Package file?

I have a bilingual parser plugin that just reads and writes files. I am now creating a package from these files and I noticed that the original files are not being added to the packages folder which makes it impossible to be used when someone imports the package. The project that gets created when someone imports the package has just the .sdlxliff files and not my custom file type.

How can I add the original files into the sdlppx package file?

Is there an API that extends the "Create Project Packages" wizard?

Thanks