Feature suggestion: Center playlist with `zz`, vim-style

[GaelicGabe]

In vim you can hit zz to center the current line in the window. Ths helps seeing the previous lines while also seeing the coming lines. This is something I'm missing in termusic, I'd like to hit zz in the playlist and have the currently selected song continue being selected but move to the middle of the window.

If there are no objections to this feature I'll fork and start working on this when I have time.

[tramhao]

Sure. I don't know how to listen to two keys. That's why I use G and g for playlist.