Add two space pawn movement

src/Pawn.java

@@ -13,8 +13,10 @@ public class Pawn extends Piece {
         ArrayList<BoardCoordinate> possibleMoves = new ArrayList<>();
         if (this.black) {
             possibleMoves.add(new BoardCoordinate(position.x, position.y + 1));
+            if (position.y == 1) possibleMoves.add(new BoardCoordinate(position.x, position.y + 2));
         } else {
             possibleMoves.add(new BoardCoordinate(position.x, position.y - 1));
+            if (position.y == 6) possibleMoves.add(new BoardCoordinate(position.x, position.y - 2));
         }
         return possibleMoves;
     }