🐍 snakegame uses a background task, and is actually playable now

[masenf]

• use rx.background_task for main game loop, so inputs stays responsive while the loop is sleeping
• use a move queue so that really fast inputs can be handled correctly
• speed up the game as snake eat more food
• better "game over" handling
• keyboard controls
• factor out common bits of UI code
• reformat the code to be more modern and nice looking
• add comments and docstrings for better understanding of how the code works

Still waiting on bug fix reflex-dev/reflex#1889 and new release before this can merge.