Stub Vulkan backend support

A lot of the architecture of the emulator here does not allow for vulkan
to initialize easily since it involves a bit of data to be exchanged
between SDL and Vulkan. This commit just adds the foundational linkage
and library code for vulkan support.

src/core/renderer_vk/renderer_vk.cpp

@@ -0,0 +1,19 @@
+#include "renderer_vk/renderer_vk.hpp"
+
+RendererVK::RendererVK(GPU& gpu, const std::array<u32, regNum>& internalRegs) : Renderer(gpu, internalRegs) {}
+
+RendererVK::~RendererVK() {}
+
+void RendererVK::reset() {}
+
+void RendererVK::display() {}
+
+void RendererVK::initGraphicsContext() { static vk::DynamicLoader dl; }
+
+void RendererVK::clearBuffer(u32 startAddress, u32 endAddress, u32 value, u32 control) {}
+
+void RendererVK::displayTransfer(u32 inputAddr, u32 outputAddr, u32 inputSize, u32 outputSize, u32 flags) {}
+
+void RendererVK::drawVertices(PICA::PrimType primType, std::span<const PICA::Vertex> vertices) {}
+
+void RendererVK::screenshot(const std::string& name) {}