[Feature Request] Support Scanning Subfolders / Sub-directories (psx and multidisc especially)

[DragonDreamVNY]

Issue Description/ Feature Request Title: Would like to be able to scan within subfolders for psx games

Background
Recent improvements with PSone emulators have support for .CHD (very compressed) or .PBP (PSP - good for combining multi-disc games into one file).
For .CHD games with multiple discs - .m3u playlists are commonly used.
In some cases I have games in [psx] -> [game subfolder], so if I scan the [psx] directory, the games in subfolders are ignored.
Tested with ISO and CHD and .m3u playlists.
These appear in YuNo if they are in the 'root' of the [psx] directory only.

example
In the | psx rom folder|

---[ .hidden or _multidisk] subFolder
Final Fantasy VII (Disc 1).chd
Final Fantasy VII (Disc 2).chd
Final Fantasy VII (Disc 3).chd

Final Fantasy VII (USA) SubFolder
Final Fantasy VII.m3u

The FFVII M3U playlist is ignored because iti s inside its own subdirectory.
Workaround 1: user moves the m3u to the root of [psx] folder

But what about users with BIN/CUE files? -> these tend to be placed within subdirectories as well.