feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

src/gx/glsdl/GLObject.hpp

@@ -0,0 +1,22 @@
+#ifndef GX_GL_SDL_GL_OBJECT_HPP
+#define GX_GL_SDL_GL_OBJECT_HPP
+
+#include <cstdint>
+
+class GLObject {
+    public:
+        // Member variables
+        GLObject* m_Next;
+        uint32_t m_RefCount;
+        int64_t m_TimeStamp;
+
+        // Virtual member functions
+        virtual void ReleaseObject() = 0;
+        virtual void AddRefTwin();
+        virtual void ReleaseTwin();
+
+        // Member functions
+        uint32_t Release();
+};
+
+#endif