[DOC]: Add process for creating a new Task handler to CONTRIBUTING.md

How would you describe the priority of this documentation request

Would be nice

Describe the future/missing documentation

This will add a new CONTRIBUTING.md section that outlines the steps for adding a new processing task type, and making it available for use via the client library and cli interface.

• Task Definition:
  • The process for adding a new task to the CLI and library, including --task specification, and configuration options.
• Processing Module:
  • How to create a new stage/module that checks a control message for a specified task, extracts the task, operates on the message payload, updates the appropriate elements, and forwards the control message to the next stage.
  • How to add the new stage/module to the pipeline
  • Setting up the module for proper unit testing.

Where have you looked?

No response