Implemented Score and Max Score Feature #1

[gauravghodinde]

fixes: #1

implementation of the logic of score is as follows

1. initialize score with zero
2. if the snake eats food increase the score by 1
3. after the death of the snake set score = 0

implementation of the logic of max score is as follows

1. initialize the maxscore with the localStorage if localStorage is null then set it to 0
2. when the snake dies if the score is greater than the max score then set it to score

video