Added '--add-description' option

[mistajase79]

This new option will add the track description to an separate *.txt file (using the same filename as the music file). Some music players will display this text whilst the track is playing - great for tracklists on DJ mixes and podcasts.

[authorisation]

Any progress on this getting merged?

[7x11x13]

Question: why only create the description file if the length of the description is > 3? Why not if it is > 0?

[7x11x13]

This is ready to be merged, when you answer my question above @mistajase79

[mistajase79]

Question: why only create the description file if the length of the description is > 3? Why not if it is > 0?

Was only to prevent adding description files if only an emoji was used - technically it shouldn't really matter, more of an edge case... happy to set to zero