Add a "Create a simple plugin" tutorial

[alexandratran]

Add a step-by-step tutorial on creating a minimal plugin for a basic use case.

The goal is to teach the user the essential workflow and components of any plugin (e.g., lifecycle events, configuration, using the API, deployment, see results – at a basic level) so they can get started quickly on their specific use case.

This topic should go under Plugins > Get started (see #1560).