Colors: Introduce color type abstraction

SFML and Dear ImGui have incompatible color types, abstract them through
a new Color class which has conversions.

Centralize color constants in a namespace as well.

World.h

@@ -10,6 +10,7 @@
 #include <SFML/Graphics.hpp>
 #include <iostream>
 
+#include "Color.h"
 #include "Player.h"
 
 enum class BlockType {
@@ -24,8 +25,8 @@ public:
     Player player;
 
     World(int w, int h,
-          sf::Color groundColor = sf::Color{67, 137, 39},
-          sf::Color ceilingColor = sf::Color{39, 69, 137},
+          sf::Color groundColor = Colors::Ground,
+          sf::Color ceilingColor = Colors::Ceiling,
           std::vector<BlockType> worldMap = {});
     int getW() const;
     int getH() const;
@@ -52,7 +53,7 @@ private:
     sf::Color ceilingColor;
 
     void fillColumn(sf::RenderWindow&, unsigned int column, float scale,
-                    sf::Color fillColor = sf::Color(84,56,34)) const;
+                    sf::Color fillColor = Colors::Wall) const;
     /**
      * Cast a ray from a given position and return its distance to the origin.
      * @param originX Ray X origin, strictly positive