Add chloropleth eGRID and NTD scripts

[jpfleischer]

efficiency.ipynb plots NTD data using UACE shapefiles. Specifically, fuel efficiency and average passengers are plotted.

chloropleth.ipynb plots eGRID data using EPA provided shapefiles. 2014, 2020, and 2022 data are visualized, including deltas across those years.

The code was written such that any external files that are needed should be automatically downloaded. The only files needed are the ntd json files which should already be checked in with this repo, if not, may need to run ntd.ipynb again.

[Abby-Wheelis]

This looks fairly clean to me! My only concern is with the chloropleth notebook there seems to be lots of duplicate code. Are both versions needed? Is there anything that could be done to cut down on that duplication?

[JGreenlee]

I'll be the first to admit that the existing notebooks are really bulky and monolithic. Extracting more of that code out into reusable functions (in script_utils.py or another file) would be a good idea.