switched up some pointers to shared, added some more rendering example

src/engine/rendering/sdl/sdlrenderer.hpp

@@ -28,7 +28,7 @@ private:
     std::unique_ptr<SdlTextureManager> texture_manager = nullptr;
     std::unique_ptr<SdlFontManager> font_manager = nullptr;
 
-    void render_texture(int x, int y, SDL_Texture *texture, SDL_Rect *src);
+    void render_texture(int x, int y, const std::shared_ptr<SDL_Texture>& texture, SDL_Rect *src);
 };