New Difficulty system!

Hello there, today I slightly reworked the Difficulty system. 

• I added a new one (extra easy). This is just a slower variant of easy.
• A map now shows on which difficulty was every level won. High difficulties mean better-cooked cookie in the map :D
• And I add a How-to-play to the menu, so you can see how to play and you do not need to read a tutorial.

Affected is just a browser version for now. Downloadable ones are still as they were for mini jam.