Add a share view for playlist

[m4dz]

Sometimes, it might be cool to share (like in Files: having a public URL) for a given playlist, so others can play on my cozy some songs I want them to discover.

Plus, this public URL can be imported in another Cozy as a source of contents, so my friends can direclty import in their Cozy my playlist.

I suggest we call it: the K7 mode 😆.

[clochix]

Another user is requesting this feature.