Error: exec: "ffmpeg": cannot run executable found relative to current directory

Hi
thanks for adding filename output option, that's very helpful!

a.
On windows Im getting this error message
[ Error: exec: "ffmpeg": cannot run executable found relative to current directory ]
although have ffmpeg.exe installed on root path of vimeo-dl and included on PATH; ffmpeg works fine if Im combining audio/video files manually

b.
docker file seems not updated with new output feature