Add support for Direct2D Compute Shaders

[rickbrew]

Filing this for ... the future :)

At some point I'll want to start dipping my toe into compute shaders so I can convert the remaining CPU-based effects in Paint.NET over to the GPU. These effects require the use of compute shaders because they need to build a local histogram.

https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/Direct2D/custom-effects.md#adding-a-compute-shader-to-a-custom-transform

[rickbrew]

I have converted my remaining CPU-based effects over to the GPU by using compute shaders. Sadly without ComputeSharp.D2D1! But that means I am eager to port my interpolated strings over to proper CS.D2D1 shader structs, and I have compute shader HLSL code that can be used to validate this effort.

(btw "eager" does not mean "omg I need it now", there's not actually any time pressure here)