Add repository context and update requirements for charting scripts

- Create `repo-context.txt` to document the repository structure, important files, setup instructions, and usage examples for the lagged oil vs. unemployment charting scripts.
- Modify `requirements.txt` to ensure all necessary dependencies are listed for the project.
- Add `saved_config.yaml` for storing configuration settings.

requirements.txt

@@ -1,5 +1,5 @@
 pandas>=1.5.0
-pandas\_datareader>=0.10.0
+pandas_datareader>=0.10.0    # good
 matplotlib>=3.5.0
 lxml>=4.6.0
 python-dateutil>=2.8.1