Openspades: Add virtual reality support

[evorios]

It will be great if the game will support VR sets using SteamVR or something like that.

[yvt]

I'm strongly interested in this idea but don't have a VR headset, so I'm marking this as help-needed.

[DrTexx]

+1 this would be absolutely excellent

I can't contribute to the codebase directly as I'm not familiar with C++, however I do own a HTC Vive.

More than happy to test alpha/beta builds if this enhancement gains some more attention in future :)

I believe VR support could probably boost the popularity of OpenSpades a fair bit too, at the very least for a brief period; the controls are simple enough that it's a really great fit.

The only thing that might require some extra consideration is the method of locomotion, since that could be a bit awkward with VR controllers unless it's well implemented (that or maybe a few locomotion options, I'd guess there are some fairly mature libraries that allow you to plug that kind of stuff in once there's a framework in place)