Allow Subtitle Downloads for Playlists

[KSMaan45]

I noticed current rewritten version of parabolic from c# to c++ has no option to download subtitles for playlist videos but chapter embed works fine as selected in main preference options not the embed subtitles, can you add the option to download/embed subtitles to playlist videos as in previous version.

[nlogozzo]

See this comment for why it was removed: #892 (comment)

We could add back the option, and it will just download and embed all subtitles available for a video...but it will not allow for you to choose or download individual languages. If you are okay with that, we could add that back.

[KSMaan45]

I'm pretty much fine with just English/Auto generated English Subtitle and won't mind even if it will append rest of too, since it will be helpful for non native English speaker like me to understand what someone says in a video with some different English accent