Make the high score persistent on users local storage

[anasM0hammad]

Currently the high score value persist in memory which means as soon as window or chrome extension gets closed the high score will be gone the next time. The idea here is to use browser persistent storage capabilities to store the high score and persist it. The high score should update accordingly in local storage and will be fetched once user starts the game again even after closing the window or extension.

[Houria-hs]

This is my first contribution to this project. Feedback is welcome.