[PROPOSAL]: `IDxbcConverter` Support

[ds5678]

Description

https://github.com/microsoft/DirectXShaderCompiler/blob/fa3fe957ea9656df75ce683c47fb2892151e4732/projects/dxilconv/include/DxbcConverter.h

Rationale

This API is useful for updating DXBC shaders to DXIL.

Proposed API

• DxcCreateInstance
• DxcCreateInstance2
• IDxbcConverter

Drawbacks

Obviously, this increases the maintenance cost of the repository.

Alternatives

I currently have hand-written bindings in my project.

Other thoughts

I am willing to make a pull request.