Add a command so users can add videos to the SoL Youtube playlist

[Gelean]

Info:

https://stackoverflow.com/questions/46476169/add-video-to-youtube-playlist-nodejs
https://developers.google.com/youtube/v3/quickstart/js
https://developers.google.com/youtube/v3/docs/playlists/insert
https://github.com/youtube/api-samples/blob/master/javascript/playlist_updates.js

Would also need to get OAuth2 working as part of this

[Gelean]

https://www.npmjs.com/package/youtube-api
https://www.npmjs.com/package/popyt
https://bbothell.rocks/popyt/docs/classes/playlist.html#addvideo

[Gelean]

Added code to help facilitate this in 77bb1d7

[Gelean]

https://bbothell.rocks/popyt/docs/classes/_entities_playlist_.playlist.html#addvideo