Add NGINX OSS development environment for testing

[kate-osborn]

What would you like to be added:
Provide a Dockerfile and instructions for developers to easily deploy and experiment with NGINX config locally.

Why this is needed:
It's often necessary to spin up an NGINX locally to test the configuration that you are adding for a feature or to debug an issue.

Acceptance Criteria

• Contributors are able to use a mechanism within the NGF repository to quickly spin up OSS NGINX, change, and test configuration.
• A method exists to be able to quickly decommission the NGINX instance.
• Documentation is created to explain the process of doing this quickly.

Dev Notes

• A makefile may be useful here