There’s nothing like a unique Airbnb to get us excited about vacation. And if it’s in a delightful shape like an A-frame? All the better. This fall, we’re planning our escape to the mountains where A-frame cabin rentals — big, small, and downright tiny — dot the landscape, and we found some of the dreamiest ones across the country. Whether you’re going leaf-peeping or booking a ski weekend, you’ll want the 13 A-frame cabins below on your radar. Hudson Valley Lake House An hour and a half north of New York City, this light and airy A-frame is surrounded by giant fir trees and overlooks a lake. With one bedroom…