Adds slime wings. The slime wings look similar to dragon wings, but are
a bit more transparent throughout, especially in the middle part of the
wing membranes, and have some drippiness to the bottom (though thats
harder to see on darker slimes)

![image](https://github.com/tgstation/tgstation/assets/102194057/f19d6d09-c475-40d2-af68-8521fec3f9ba)

![image](https://github.com/tgstation/tgstation/assets/102194057/7a8fc450-9011-46d4-ba1b-acd836e51b25)

If even flies and skeletons can get wings - why not slimes? Especially
since xenobiologists which often end up as slimepeople can make the
flight potion via xenobiology.
:cl:
add: Slimepeople can now get wings from flight potions.
/:cl:

 into slime-wings