Document basic ffmpeg examples for transcoding the resulting file MP4/AAC

[morgant]

I'd like to add an example of transcoding the lossless file, including scaling, to the README. For example, one of my recent tests was transcoded, as follows (though I don't know if this was a good way of doing so):

ffmpeg -i Downloads/DMSI-1021-Demo-Take00.mkv -c:v libx264 -preset veryslow -crf 0 -vf "scale=1200:-1,format=yuv420p" -movflags +faststart -c:a aac Downloads/DMSI-1021-Demo-Take00.mp4