Create shadow render pass

gpu.h

@@ -28,6 +28,7 @@ typedef struct {
 	VkShaderModule frag_shader;
 	VkDescriptorSetLayout desc_set_layout;
 	VkDescriptorPool desc_pool;
+	VkRenderPass shadow_pass;
 	VkRenderPass render_pass;
 	VkPipelineLayout floor_pipeline_layout;
 	VkPipeline floor_pipeline;