Add global width data

[MaddeeRubenson]

This adds the global width datasets to data discovery (width-dataset-exploration.Rmd). I found that the Merit dataset was much more robust and useful in this exercise so that dataset was added to the data-discovery.Rmd file for processing with the other COMID attributes.

The other dataset (global width dataset) is joined to COMIDs and can be used if needed but is much less robust and the numbers seem off compared to Merit

[skylerlewis]

@MaddeeRubenson Added a few comments above, otherwise looks great

[skylerlewis]

@MaddeeRubenson Good to merge I'd say!