Add PyPI example to Getting Started documentation (#685)

As the title describes, adds a PyPI example as a target for the
analysis.

Signed-off-by: Eric Brown <eric.brown@securesauce.dev>

docs/getting-started.md

@@ -41,6 +41,12 @@ Run precli against all the python test examples:
 precli -r tests/unit/rules/python/
 ```
 
+Run precli against an entire PyPI repository:
+
+```
+precli -r https://pypi.org/project/precli/
+```
+
 Run precli against an entire GitHub repository:
 
 ```