Minor updates on the alpha

Thanks you so much for the warm welcome you give to the game, we're still working on it, and here's the first patch !

Fix following bugs :

-When the notes speed was very high, the player was able to hit them even before their apparition.

-When changing level or going to the main menu and launching a level afterwards. The music didn't played.

Minor adjustments:

-Fix text on the title screen

-Replace the quit button by a retry button on the pause menu

-Get rid of the quit button on the webGL build

Have fun playing it !