Incorrect windowing for pitch ratios less than 1

[MysteryPancake]

Hello!

Firstly, thanks very much for this implementation. It has really helped me understand PSOLA!

However, I found a bug in the windowing. It is best explained by this diagram:

The issue is due to the windowing being incorrect for all pitch ratios lower than 1.
In this case, the peaks array must be used to calculate windowing, requiring different math.

I've put a bit more explanation on Stack Exchange.