[Doc][argocd] missing docs

## Documentation Scope
the docs are missing a guide for the new argocd plugin

## Describe the Change
docs about new argocd plugin

## Screenshots
If applicable, add screenshots to help explain your thoughts.

## Additional context
Add any other context about the problem here.

Start by locating the existing plugin documentation and the new argocd plugin entry point. Define the guide's required setup, usage, and configuration content from those sources; done means users can follow the guide to use the plugin.

Written by the indexing model from the issue text.