Set up multisampling

gpu.h

@@ -39,6 +39,9 @@ typedef struct {
 	VkDescriptorSetLayout floor_desc_set_layout;
 	VkDescriptorSetLayout desc_set_layout;
 	VkDescriptorPool desc_pool;
+	VkImage colour_img;
+	VkDeviceMemory colour_mem;
+	VkImageView colour_view;
 	VkRenderPass shadow_pass;
 	VkRenderPass render_pass;
 	VkDescriptorSet floor_desc_sets[MAX_FRAMES_IN_FLIGHT];