Update gx-1.0.0a4 README with S3 dataset info.

gx-1.0.0a4/README.md

@@ -4,12 +4,14 @@ Demos of expectation authoring and validation workflows for great-expectations 1
 
 These demos use python 3.10 with [1.0.0a4](https://pypi.org/project/great-expectations/1.0.0a4/).
 
-## Notes about these scripts
-The scripts in this directory will run against 1.0.0a4, and include TODOs on future changes planning for subsequent prereleases of 1.0.0.
+## Notes about these demos
+
+* The scripts in this directory will run against 1.0.0a4, and include TODOs on future changes planning for subsequent prereleases of 1.0.0.
+* To run the `demos/scripts/*.py` scripts, one must have valid AWS credentials for free access to the [New York City Taxi Data Set](https://registry.opendata.aws/nyc-tlc-trip-records-pds/) since it is served from S3. See the linked data set description for more information.
 
 ## Getting started
 1. Create a virtual environment: `python -m venv .venv`
-1. Source the virtual environment: `source .venv/bin/activate`
-1. Install requirements: `pip install -r requirements.txt`
-1. Start the postgres container: `../scripts/run_dockerized_pg.sh`
-1. Run the notebooks in `demos/`
+2. Source the virtual environment: `source .venv/bin/activate`
+3. Install requirements: `pip install -r requirements.txt`
+4. Start the postgres container: `../scripts/run_dockerized_pg.sh`
+5. Run the notebooks and scripts in `demos/`