Add Canvas

Canvas contains the RenderTexture2D
contains the Tree
and now it's eazy to add more modules

inc/App.hpp

@@ -1,5 +1,5 @@
 #include <vector>
-#include "Tree.hpp"
+#include "Canvas.hpp"
 
 class App
 {
@@ -15,7 +15,7 @@ public:
 private:
   int pos = 0;
   int screenWidth, screenHeight;
-  std::vector<Tree> trees;
+  std::vector<Canvas> canvases;
   Vector2 center;
   float rotation = 0.0f;
   Rectangle destB;