readme and first steps for storage buffer raytracing

src/app_data.rs

@@ -34,6 +34,9 @@ pub struct AppData {
     pub uniform_buffers: Vec<vk::Buffer>,
     pub uniform_buffers_memory: Vec<vk::DeviceMemory>,
 
+    pub storage_buffers: Vec<vk::Buffer>,
+    pub storage_buffers_memory: Vec<vk::DeviceMemory>,
+
     pub descriptor_pool: vk::DescriptorPool,
     pub descriptor_sets: Vec<vk::DescriptorSet>,