Cairn monster stats doc added

Monster stats now provided in a separate doc for the game Cairn. Today when thinking about this adventure, I kept wanting to add some stats for the monsters. Cairn came to mind as pretty quick to do this with. And, I love that game. I was also thinking of doing some for OSE, or maybe something else. For now, I think these are helpful to get a little more sense of the monsters, whether you are using Cairn or another system.