Feature Request: Structured/Machine Parseable Output

[Walt280]

The basic idea would be to have a command-line flag that can be set in order to allow ytarchive to output progress/information that would be easier to parse in scripting/programming then the current logging output. It should be possible to leverage the slog package for this, with the added benefit of being able to select between key-value or json output.

So for example:
Video Fragments: 1111; Audio Fragments: 1111
would become something like:
video_fragments=1111 audio_fragments=1111 or {"video_fragments": 1111, "audio_fragments": 1111}

If there is interest for this, I can try and implement this. If this is already possible with the current codebase, I would appreciate any pointers.