Proposal: Support set encoding format in CLI

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Feature Request

I'm developing an app to play cutscenes and found PCM audio cannot decode in WinUI. I can export video and audio separately and combine them into mkv files after encoding. However, it's the best way to finish all steps in CLI.

Code Design

Add two command option --audio-format and --video-format to command demuxUsm and batchDemux.

Options description:

# GICutsences.exe demuxUsm -h
Options: 
  -af, --audio-format <audio-format>           Encode audio stream in MKV file, the original format is PCM.
  -vf, --video-format <video-format>           Encode video stream in MKV file, the original format is VP9.
  # other options ...

These two options will take effect only after adding --merge. If user don't add any encoding format, the origin stream would be copied to output file. If user add encoding format, program will use ffmpeg engine instead of --mkv-engine.

Usage Example

GICutsences.exe demuxUsm <InputFile> -af aac -vf h264 -o ./
Ignore -af and -vf option because of no -m

GICutsences.exe demuxUsm <InputFile> -m -af flac -o ./
Audio stream will be encoded to flac format.

GICutsences.exe demuxUsm <InputFile> -m -af flac -e mkvmerge -o ./
Ignore -e mkvmerge, use ffmpeg insead.

Known Problem

When add --video-format, it takes a lot of time to encode video stream and shows no progress. But I think nobody would re-encode video stream.