[DOC]Getting started guide - how to contribute an addon

[bryantbiggs]

Provide documentation to help guide users on how to contribute an addon to avoid PR feedback churn. Some things we should look at including are:

• What are the common pieces required for an addon (i.e. - add chart to addon chart repo first)
• What is the standard "structure" (main.tf, outputs.tf, variables.tf, versions.tf, README.md) -> could probably create a template dir to copy+paste and update
• What content is required in the README.md -> ensure commands for testing/validating addon are included
• High level guidance on what should go into the addon module and what should be left out for implementation
• Any conventions (naming conventions, defaults, etc.)
• What should be in the addon README.md and what should be updated under doc/s

Anything else I might be missing?

[Zvikan]

Consider adding any tips,tricks and tools that makes our development cycles easier, e.g. pre-commit using locally or relying on the GH workflows.

[florentio]

Hello. I am volunteer to propose something for this issue. feel free to assign it to me if anyone else is not working on it right now and I will propose something very soon