Add a kind of musics marketplace

[utarwyn]

In the latest release of the plugin, we can import musics from the musics folder or from a link, that's nice. But servers owners have to search for working NBS files and it can be a pain. So a pretty cool feature would be to integrate a marketplace directly inside the plugin to search and download songs: easy, quick and only working NBS files.

For now, you can use these links to download NBS songs:

• https://github.com/thatcraniumguy/Songs/tree/master/NBS%20files
• https://hielkeminecraft.github.io/OpenNoteBlockStudio/songs/