Option to specify separate directory for download and final output

[sirinsidiator]

I'd like to somehow keep the incomplete files and the final output from ffmpeg in separate directories, so I can load the files into jellyfin without any clutter. I've checked the readme, but didn't see anything that would allow me to achieve that, so maybe an option --working-directory/-wd and --output-directory/-od which are prepended to the value specified by --output could be added? When no working directory is specified it would use output directory for both cases and otherwise it would just default to an empty string and work like in the current version.

Being able to run a command like proposed in #62 would allow a similar result, but I feel having these options could still be worthwhile.