Document common workflows of weather-tools

[alxmrs]

After #7 is complete, we should prepare a "cookbook" of common dev-ops workflows that use weather-tools. These should include:

• A walkthrough of using each tool in context with each other on GCP.
• How to use weather-dl to download priority data first.
• How to schedule dataflow jobs in the future (if possible).
• How to set up Alerts and monitoring Dashboards in GCP.
• (reach) using a Cloud Montoring dashboard to view results from the Download Manifest.

[mccloskey]

Can you please also document how to choose the value of the 'dataset' field in the .cfg file? Or even better, autosuggest values based on the requested ECMWF data fields specified elsewhere in the .cfg file.

For example, some fields (eg 'ttr', 'tsr') are documented by ECMWF to be "single-level", where the 'dataset' field would be called reanalysis-era5-single-levels instead of reanalysis-era5-pressure-levels as shown in the currently checked-in example .cfg files.

I'm guessing, but looks like at the moment, one should inspect the ECMWF URL describing the dataset and use the last part of the URL path, eg: https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-pressure-levels