Add initial (trivial) pubsub module and faas module that supports pubsub

Relates #3 (closed)

Follow up MRs or split tickets for alerting and working dead letter queue

CHANGELOG.md

+# Change Log
+
+## [0.2.0]
+
+### Added
+
+- Additional example functions
+- Basic exception handling for functions
+
+### Changed
+
+- Removed/renamed example functions
+- Change test tooling function naming, `event_app_client` => `event_app_test_client_factory`