Add tests for all examples

## Summary

Add pytest coverage for every example in this repository.

The current test file is here:

https://github.com/adewale/python-workers-examples/blob/main/tests/test_examples.py

Some examples already have coverage, but the suite should eventually include a smoke or functional test for each numbered example so regressions are easier to catch.

## Notes

This issue is just a placeholder/tracking issue. I plan to add the missing tests later.