Keep the level set when the turn restarts or even when the browser is closed

[Maike Negreiros]

When the user click the "play again" button, the game level is reset to medium. The same issue happens when the browser is closed and opened.

[Maike Negreiros]

Fix: #40

[Unclebigbay]

try using Javascript localstorage

[Maike Negreiros]

If you look into the referenced PR, you'll see I'm using localstorage