Preprocess urls before hitting them in the playlist, keep a more detailed playlist

[Lartza]

Is your feature request related to a problem? Please describe.
Currently the bot keeps a list of urls as it's playlist, and processes the song when it hits it in the playlist.

Describe the solution you'd like
Add music to playlist only after it has been fully processed (with full information of the song, url, title and the path). Download songs the moment they are added and possibly keep a processing queue to prevent messing the processing with fast duplicate requests.

Describe alternatives you've considered
I haven't, feel free to have a think.

Additional context
Keeps playback interruptions to a minimum and I feel like would improve the flow of #15

[azlux]

it's into my Todo list. I think it's better to download music when it's added.
So I will download only the next music for now !

[azlux]

Working on my beta bot, on github in few days

[azlux]

Until I finish the code, you can check the branch : https://github.com/azlux/botamusique/tree/dev , all info are download at the moment we add a music.

[azlux]

now on master branch