[downloader] plugin overhaul

[Araxeus]

Replace ytdl-core with YouTube.js

• Increase download speed to max (for me it's a 10x increase, can be potentially a much bigger increase based on net speed)
  fix Download speed slowed down #1051

• Add album to id3 when available

• Add trackId to id3 when downloading an album

• Add skip existing files option
  fix [Feature request] Make playlist download not download already downloaded songs #319

• Make download button show up only if there is a radio or shuffle button in the same menu

• add helpful error when trying to download a private or “Mixed for you” playlist

• Make the options synced between back.js and menu.js (Remove the need to restart the app to apply plugin settings)

• Remove chokidar dependency and handle the progress reporting in a more fluid way
  (progress now also report on the FFmpeg conversion progress, and also the playlist download progress updates based on the percentage of the current downloading item)

fix #1010, fix #768, fix #453, fix #903, fix #297, fix #636, fix #818, fix #622, fix #570, fix #610, fix #556, fix #882

now downloading and converting happens on the main process instead of the renderer, allowed by: nodejs/node#45074

also as before - allow opus instead of mp3 with the drawback of having no id3 metadata

TIP: Try setting the codec option to opus, then download a playlist, it's 20x times faster than encoding to mp3 - and the progress bar looks really smooth because of increasePlaylistProgress() 😉

[MulverineX]

add helpful error when trying to download a private or “Mixed for you” playlist

Ideally youtube.js gets auth support eventually, this is quite a pain

Great work on this!

[Araxeus]

@th-ch I don't know what it did exactly, but I assume the fix from https://github.com/th-ch/youtube-music/pull/854/files isn't needed anymore since we are on back.js right?

[Araxeus]

@th-ch @MulverineX @Zo-Bro-23 @DereC4 did any of you test this on a non-windows machine?

[DereC4]

@th-ch @MulverineX @Zo-Bro-23 @DereC4 did any of you test this on a non-windows machine?

Let me load this up on the lab computers at our department and give it a try

[th-ch]

Looks good overall! It just seems a function is not exported and should be

[Araxeus]

Fixed, thank you for the review :)