Add support for custom shaders

[SirLynix]

I was thinking, there already are plugins that brings support for shaders to OBS Studio, but due to the fact that they apply after this plugin renders, none of them is able to use the depth map and such. It would be nice to add a way to have that.

Also a way to have some augmented reality stuff.

[skarard]

This is a great idea! I was tweaking the greenscreen composite with a shader to clean up the output. It would be great to have access to the depth map!

[SirLynix]

I you have some idea on how to cleanup the greenscreen shader output I'll be glad to help you integrate them in obs-kinect!