Add an example script to show GEOS-CF workflow

[tsherwen]

Add an example script to show the operation workflow taken for the ARNA campaign using output from the NASA GEOS-CF 5-day global 25 x 25 km forecasts.

GEOS-CF and GEOS-5 were used to decide where to fly the aircraft on a specific day during the ARNA campaign. It could be useful for others to give a quick example of how this code was used to manage and automate diagnostics and forecasts (e.g. Dust, visibility, satellite, etc) into a single Google Drive folder for the mission scientists and flight planning team.

All the code is openly provided here (inc. operation chron job script - do_campaign_operation_forecast_plots.py), however, an interactive note could be more accessible.