Create simple demo app using KTX & CMake

[MarkCallow]

We should create a demo app using KTX (outside of this repo) that is as simple as possible and based on CMake. This gives the programmer's perspective.

[wh1t3lord]

I hope you can add some d3d12 example in this case

[tuket]

That would be very useful. I have spent quite a lot of time trying to integrate this library into my CMake project without success.