Get the address of the vkGetInstanceProcAddr function.
This should be called after either calling SDL_Vulkan_LoadLibrary() or
creating an SDL_Window with the SDL_WINDOW_VULKAN flag.
The actual type of the returned function pointer is
PFN_vkGetInstanceProcAddr, but that isn't available because the Vulkan
headers are not included here. You should cast the return value of this
function to that type, e.g.
Get the address of the vkGetInstanceProcAddr function.
This should be called after either calling SDL_Vulkan_LoadLibrary() or creating an SDL_Window with the SDL_WINDOW_VULKAN flag.
The actual type of the returned function pointer is PFN_vkGetInstanceProcAddr, but that isn't available because the Vulkan headers are not included here. You should cast the return value of this function to that type, e.g.
`vkGetInstanceProcAddr = (PFN_vkGetInstanceProcAddr)SDL_Vulkan_GetVkGetInstanceProcAddr();`