dev_cross_indicators

Hi @vagudets @nperez

I've created a new branch called 'dev_cross_indicators' with the code I produced to compute the calibrated seasonal forecasts of frost days and the number of consecutive days exceeding a threshold.

I haven’t opened a merge request yet, as the code still needs some improvements. It would be great if we could review it together, so we can discuss what enhancements should be implemented.

I’ve uploaded it now in case it’s useful for anyone else in the meantime (e.g. @ptrascas).

Thanks

Vero