Create sprites/animations for "pony" prototype

[the-emerald]

Create sprites and animations for the current prototype "pony" placeholder.

[the-emerald]

Research notes:

• height and width define the height and width of the sprite in the spritesheet
• The game will look right line_length times, then it will start left again, but this time under the other row of sprites. It will do so until it reaches frame_count number of sprites. This is for non-RotatedAnimation
• For RotatedAnimation, the direction_count is how many rows (and directions) there are and the frame_count is how many frames there are per row. The line_length property doesn't exist, the rest is the same as Animation (or at least seems like the same).
• shift is used to offset the sprite in-game from its bounding box.