Cross platform support

[hnisula]

• Compile-time switching between d3d12 and vk
• Support linux socket
• Add glfw window
• Add glfw input handling
• Add vk fundamental rendering set up (rhi, device, queues)
• Add vk swap chain
• Fix vk syncing in a way that can be used for both d3d12 and vk
• Add hlsl->spir-v->vk shader compilation for vk
• Add vertex/index buffer for vk
• Fix font rendering for vk
• Fix gui rendering for vk
• Make sure the mathematics and shaders work as expected for vk

Closes #68