Improved performance and title artwork finalization

Hi!
I have taken a look at what was causing some of the FPS issues inherent in the initial release and made a few tweaks accordingly. You can now also find both a "high" and "low" quality version of the game, which currently changes which shaders are used for foliage and water. Lastly, I have also finalized the title artwork for MonsterStone Prelude and added it to the main menu, trailers and itch.io page!