Add notebook: Compare crop time series to observations

[samsrabin]

Description of changes:

Adds a notebook to compare time series of crop yield and production to observation data. Works only on raw annual CTSM outputs, not time series files.

There's a fair amount of work remaining that I won't track here, so I don't have to-do lists in two places.

Standard questions

• Have you followed the guidelines in our Contributor's Guide?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you made sure that the pre-commit checks passed (#8 in Adding Notebooks Guide)?
• Have you hidden the code cells (#8 in Adding Notebooks Guide) in your notebook?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully tested your changes locally?
• Have you moved any observational data that you are using to /glade/campaign/cesm/development/cross-wg/diagnostic_framework/CUPiD_obs_data and ensured that it follows this format within that directory: COMPONENT/analysis_datasets/RESOLUTION/PROCESSED_FIELD_TYPE?

[samsrabin]

• Point this to the upstream repo once I've merged my cupid-crops-work branch.