Please review the two documentation files

[yuqiww]

I created two files for documentation purposes:
README for the folder structure of this repository : https://github.com/BayAreaMetro/onboard-surveys/blob/master/README.md
README for onboarding data processing steps: https://github.com/BayAreaMetro/onboard-surveys/blob/master/make-uniform/production/README.md

Would you please check and make necessary edits?

Particularly, for the reference files, I'm not sure about "rail_names_inputs.csv" and "Passenger_Railway_Stations_2018.shp".
Also, did I miss any reference file?