Enhancing to multiple levels

[SithuminaBhagya]

https://github.com/SithuminaBhagya/Sokoban-Java.git

Above I have modified your code so that multiple levels are possible. Also after each successful completion of a level number of steps the player is completed is displayed. you only have to change one line to change the number of levels and then add the layout accordingly. hope anyone find this useful. cheers !