add the option to choose subtitle language

[christiansievers]

Thanks for the very useful tool! One idea: Your script could be English by default, and use other languages when needed.

It would be great if your script could let me add (i.e.) - lang=cn to the command line, adding --sub-lang=cn to the yt-dlp command. So that the resulting html file uses the language specified.

[TenoTrash]

This will be a very nice option! Cheers from Argentina

[obra]

I'd happily take a PR for this

[TenoTrash]

I made some modifications to add llanguage option at the end of the command line. Maybe adding a default US language later?
Cheers!