[Square] Make constructor public

Square.hpp

@@ -26,6 +26,9 @@ public:
     static Optional fromIndex(Index index);
     static Optional fromName(const std::string &name);
 
+    Square(Index index);
+
+
     Coordinate file() const;
     Coordinate rank() const;
     Index index() const;
@@ -40,9 +43,6 @@ public:
     static const Square A8, B8, C8, D8, E8, F8, G8, H8;
 
 private:
-
-    Square(Index index);
-
     Index mIndex;
 };