Add SDL_Window to initGraphicsContext prototype

This value is needed for vulkan to properly allocate a surface, and would benefit OpenGL to move more of its initialization code into here rather than in `emulator.cpp`.

src/core/renderer_null/renderer_null.cpp

@@ -5,7 +5,7 @@ RendererNull::~RendererNull() {}
 
 void RendererNull::reset() {}
 void RendererNull::display() {}
-void RendererNull::initGraphicsContext() {}
+void RendererNull::initGraphicsContext(SDL_Window* window) {}
 void RendererNull::clearBuffer(u32 startAddress, u32 endAddress, u32 value, u32 control) {}
 void RendererNull::displayTransfer(u32 inputAddr, u32 outputAddr, u32 inputSize, u32 outputSize, u32 flags) {}
 void RendererNull::drawVertices(PICA::PrimType primType, std::span<const PICA::Vertex> vertices) {}