ADD option to autocrop black(ish) bars from videos

[allanlaal]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

often black bars are added to portrait videos to center the square Short or tiktok or whatever. or its a byproduct of shitty re-recording.

Why do you want this feature?

1. square screens: I have a square screen. There is nothing worse than when theres a square video turned into portrait with black bars, so you I watch a small square move in the center of my phones square screen :D

2. ability to vertical align square videos on portrait phones, so that instead of the black bars the users sees the first few comments or description or whatever

3. AMOLED (Amoled support #4148) screens can use true black

Additional information

mpv already has an autocrop script and its great for aligning movies to the top of the screen on my projector

the ffmpeg filter: https://ffmpeg.org/ffmpeg-filters.html#cropdetect

I think this should default to enabled - discuss below