Added example on 2d lists and changed format (#23665)
Added example on 2d lists and changed format (#23665)

updated the code format along with an example of 2d list.
BhaveshSGupta/FreeCodeCamp,raisedadead/FreeCodeCamp,BhaveshSGupta/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp,jonathanihm/freeCodeCamp,jonathanihm/freeCodeCamp,BhaveshSGupta/FreeCodeCamp,raisedadead/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp