Enable directory structure for gcode files

[marekvse]

Is your feature request related to a problem? Please describe.
Not being able to browse a folder structure is a serious shortcoming of the software. Having to save everything, for every type of filament, every nozzle diameter etc. into a single root directory that, on top of that, won't show the file names that are even of just medium length is something I could not believe was not taken care of during development.

Describe the solution you'd like
The ability for the firmware to read the folder structure of the card and easily move within it to select the file to be printed.

Describe alternatives you've considered
I am saving my files to a folder structure, but to print anything I need to use a computer to copy them to the root of the card and usually rename it to indicate for which filament it is meant. That is a terrible solution, but the only one I can solve this problem with as far as I can see.

Additional context
I have a much older 3D printer from another brand and they do have this ability from the very start. This is the first ever computer-based device that works with files that I've ever seen to not work with folders.