[PR] Adds a shelterfrog spacebux purchase

[Munien]

I don't have much of a frog in this race, I personally don't care about the poison thing of many of the other things surrounding shelterfrogs as a whole, but I can't say I like the idea of mutantraces being paywalled by spacebux. This might have been fine 5 or so years ago but it doesn't really fall in line with current mutantrace standards imo. I do hope we get to see some implementaion of them soon back ingame though