Incorporate more easing functions and demo the ones available

In the animation.py file there is a number of easing functions available that the game relies on.

It would be great if I can incorporate more easing functions to provide more options for animating the sprites, as well as adding a demo of all functions available.

Start by reading animation.py to inventory the existing easing functions and understand how sprites use them. Identify where the project demonstrates animation, then add more easing options and a demo covering every available function; done means the functions are usable and all are demonstrated.

Written by the indexing model from the issue text.