Compress output files

Even if let-it-snow outputs are not really big compared to other products, it is alsways a good pratice to use optimized file formats as ouput.

Minimum would be to apply some compression on TIF outputs, this should be easily done, and every library for writing or reading TIF already support this.

Check if using Cloud optimized GeoTIFF makes sense here.

This could be an option first, but at some point the default.