Comment # 7 on bug 1201474 from Stefan Dirsch

In sway packages I see requires to

  libGLESv2.so.2()(64bit)

and this again is linked against 

  libGLdispatch.so.0

So there is no hard requirement to Mesa or other GL drivers (by intention). I
think you can run into this only when choosing a minimal installation. I can't
say whether sway works with nVidia's proprietary drivers. Haven't tried this.
But I think recommending Mesa-dri 
wouldn't hurt in sway package.