Respawning animation is now implemented!  Unfortunately, there exists no BitBotSpawnSpriteSheet for the enemy robots, so the enemy robots borrow player sprites for now.
Added the shadow to the Sprite.
Updated the command prompt image.
Not a very good commit - added move and respawn sfx, but it's not complete yet.
Added a function to check for items beyond twice the game's canvas' height
Several fixes:  added the actual Sprite Shadow image, introduced a more complete sprite sheet image, and fixed the "executing" sound effect that was not starting/stopping properly.