Bug: folder names starting with _* are not ignored

[stromseng]

Example:

These are not routes according to https://nextjs.org/docs/app/building-your-application/routing/colocation#private-folders

[DiiiaZoTe]

These were introduced later on in new versions of Next.js. I don't necessarily have the time to update the package. Feel free to do so! This one shouldn't be too bad tbh...Maybe just skip the folder and all subfolder in the recursion that gathers the folders.