[Feature] Recursive folder scanning

[BobGallardo]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
Add recursive scanning in rom folders.

Describe alternatives you've considered
Re-organize some of my platform folders into a flat structure instead of some using additional organization within a platforms rom folder.

Additional context
I have some large rom collections that are organized with subfolders by region. Sometimes it doesn't make sense to have thousands of roms in a single folder.

[gantoine]

Sometimes it doesn't make sense to have thousands of roms in a single folder.

Sometimes the world doesn't make sense 🙂
Our rigid folder structure allows for easy parsing of multi-file roms. Since there's no standard for rom file organization, mandating a single folder/platform is the best we can do.