example/filesystem: Add directory listing example
example/filesystem: Add directory listing example

AdaCore/Ada_Drivers_Library,simonjwright/Ada_Drivers_Library,simonjwright/Ada_Drivers_Library,ellamosi/Ada_BMP_Library,Fabien-Chouteau/Ada_Drivers_Library,AdaCore/Ada_Drivers_Library,Fabien-Chouteau/Ada_Drivers_Library,lambourg/Ada_Drivers_Library