Allow setting location of the hashes.json and optimized images

[stavros-k]

I want to move the hashes json and optimized in a custom dir so I can cache them in my CI.
This dirs should be used afterwards to check if the image is there and copy it to the exportPath instead of re-optimizing it.

The reason I want a custom path, is that I have quite a few websites, that 90% of the images are shared.
So having a shared cache, improves things by a ton.

Ignore the many edits, it was moments that I thought I found something but then I didn't

Thanks!