add ocean biogeochemistry variable list for Med-CORDEX

[sam-somot]

@larsbuntemeyer @jesusff :
I'm opening here an issue to start the discussion on the ocean biogeochemsitry variable list we need to create for the Med-CORDEX initiative. Please @mreale @ssalon ... go head on this topics when you are ready.

[jesusff]

Wrong Marco (@mcreal82); not sure about Stefano. Please, don't make up usernames or you will notify random people. Maybe they are interested in regional climate modelling... 😃

This case is similar to #70, we could add the ocean_biogeochemistry component to the existing Med-CORDEX data request https://github.com/WCRP-CORDEX/data-request-table/blob/join-components/data-request/dreq_MED.csv