Add basic app interface

- Add pool struct for data pools

src/main.cc

@@ -5,8 +5,8 @@ int main() {
 
   Window w({800, 600}, "Render Test");
 
-  ImageID img = w.load_image("./assets/images/arrow.png", true);
-  FontID font = w.load_font(
+  int img = w.load_image("./assets/images/arrow.png", true);
+  int font = w.load_font(
     "./assets/fonts/charybdis.ttf",
     24,
     false,
@@ -15,7 +15,7 @@ int main() {
     true
   );
 
-  TextID text = w.create_text(font, "Hello Engine", 12, {255, 255, 255, 255});
+  int text = w.create_text(font, "Hello Engine", 12, {255, 255, 255, 255});
 
   float t = 0.0f;