Add bindings for glfw Vulkan functions

[Fincap]

Added bindings for remaining unimplemented Vulkan functions:

• glfwGetInstanceProcAddress
• glfwGetPhysicalDevicePresentationSupport
• glfwCreateWindowSurface

Library user will need to supply their own instance, device, surface, and allocation callback pointers. The types for Vulkan objects VkInstance and VkPhysicalDevice are just aliased to ?*const anyopaque, and the types for Vulkan structs VkAllocationCallbacks and VkSurfaceKHR were aliased to anyopaque. The main intent of these aliases is to provide clarity on the expected Vulkan types and ensure the bindings function signatures are mostly aligned with the glfw API (https://www.glfw.org/docs/3.3/group__vulkan.html).

I've tested getInstanceProcAddress to confirm that it retrieves function pointers correctly, and that those function pointers can be called correctly when cast to the command signature, however I didn't go all the way to creating a new Vulkan instance because I don't have the SDK set up on my current computer.

Fixes #18

[Copilot]

Pull Request Overview

This PR adds Zig bindings for three remaining GLFW Vulkan functions to enable Vulkan surface creation and function pointer retrieval. These bindings provide a complete interface for using GLFW with Vulkan in Zig applications.

• Added type aliases for Vulkan objects (VkInstance, VkPhysicalDevice, VkAllocationCallbacks, VkSurfaceKHR)
• Implemented bindings for glfwGetInstanceProcAddress, glfwGetPhysicalDevicePresentationSupport, and glfwCreateWindowSurface
• Added proper error handling for all three functions following the existing pattern

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