Event Listener - Containerize / GHA to complete containerization

[franTarkenton]

Taking the existing demo code that currently is listening for events and:

• create a dockerfile
• create a github action that will build the image and cache it in a container registry - likely github container registry
• think through a strategy for tagging

[franTarkenton]

dockerfile created and action created to build docker image and publish it to the github container registry.

pr: #18