Missing Pet Icons, Resting Graphics

### Features ###
* 2 new missing pet pixely icons
* Resting Zzzs 

### Notes ###
* I've changed the pets.html to use one of the new missing pet icons
* There are 2 solutions for the missing pet icon feel free to play and pick the best one or revert back to what we currently are using
* In addition to the Zzz icon added to shop_sprites, I threw in some closed eyes art that'll require some CSS positioning to get in the correct place. Mostly just added this for playing with / testing since I thought it would be neat if the avatar had their eyes closed as well. Will only work with one skin colour type and if implemented the closed eyes would probably reside in a different sprite sheet.