Create shadow pipeline

gpu.h

@@ -37,6 +37,7 @@ typedef struct {
 	VkPipelineLayout floor_pipeline_layout;
 	VkPipeline floor_pipeline;
 	VkPipelineLayout model_pipeline_layout;
+	VkPipeline shadow_pipeline;
 	VkPipeline model_pipeline;
 	VkCommandPool cmd_pool;
 	VkCommandBuffer cmd_buf;