Automatic transcription: a way for video publishers to choose to enable it or not, video per video

[JohnXLivingston]

Describe the problem to be solved

Peertube v6.2.0-RC1 comes with the new automatic transcription feature, to generate subtitles.

But some videos don't need subtitles (music show, video without people speaking, ...).
Or maybe, the publisher has subtitles that they will publish later (maybe just after the upload, maybe 2 or 3 days later).

In v6.2.0-RC1, transcription will be automatic for all videos, even if not needed/wanted.

Describe the solution you would like

There should be an option in the video upload form, to choose if we want to generate automatic subtitles.
This option could be checked by default.