Fixed a missing include when compiling openxr_platform.h using OpenGL instead of D3D
#elif defined(XR_USE_PLATFORM_WIN32) && defined(XR_USE_GRAPHICS_API_OPENGL)
#include <windows.h>
+#include <unknwn.h>
#define XR_GFX_EXTENSION XR_KHR_OPENGL_ENABLE_EXTENSION_NAME
#define XrSwapchainImage XrSwapchainImageOpenGLKHR
#define XR_TYPE_SWAPCHAIN_IMAGE XR_TYPE_SWAPCHAIN_IMAGE_OPENGL_KHR
