Save partial progress on exposure workflow

[carlosgjs]

E.g. save transformed climate data to disk in case the process needs to be restarted.

Pseudo-code:

   if exists('climate_tibble.rds'):
        climate = load('climate_tibble.rds')
   else:
        climate = convert_to_tibble(climate)
        save(climate, 'climate_tibble.rds')