adding open/save project and changing layout

engine/canvas.h

@@ -19,6 +19,11 @@ public:
     struct Snapshot
     {
         std::unique_ptr<uint8_t[]> image[6];
+        void create(int w, int h)
+        {
+            for (int i = 0; i < 6; i++)
+                image[i] = std::make_unique<uint8_t[]>(w*h*4);
+        }
     };
     bool create(int width, int height, std::string name);
     void clear(const glm::vec4& c);
@@ -79,6 +84,8 @@ public:
     void snapshot_restore();
     void clear_context();
     void save(std::string data_path);
+    void save_project(std::string data_path);
+    void open_project(std::string data_path);
 };