Enable back-face culling

gpu.c

@@ -537,7 +537,8 @@ void gpu_init(gpu_ctx_t *ctx, const gpu_config_t *config, model_t model)
 		.rasterizerDiscardEnable = VK_FALSE,
 		.polygonMode = VK_POLYGON_MODE_FILL,
 		.lineWidth = 1.0f,
-		.cullMode = VK_CULL_MODE_NONE,
+		.cullMode = VK_CULL_MODE_BACK_BIT,
+		.frontFace = VK_FRONT_FACE_CLOCKWISE,
 	};
 
 	// Populate multisampling configuration