SwiftShader doesn't copy vk_swiftshader_icd.json to output directory

# Summary
`Silk.NET.Vulkan.SwiftShader.Native` copies only the native library but doesn't copy the vk_swiftshader_icd.json file (which is necessary to use SwiftShader with `VK_DRIVER_FILES`).

Optional (not sure if necessary): SwiftShader still generate json file with `"api_version": "1.0.5"` but I think it should be 1.3.0.

# Steps to reproduce
- Platform: Desktop
- Framework Version: .NET Core 3, .NET 4.8, Xamarin Android 8.1
- API: Vulkan
1. Reference `Silk.NET.Vulkan.SwiftShader.Native`
2. Build project
3. Check output dir