docs: implement Odoo Addons README and extensibility overview

[D3n3bX]

Description

This PR adds the high-level README for the Odoo Addons directory, emphasizing the generic and extensible nature of the Perry integration.

Fixes #18

Key Content

• Infrastructure Overview: Details the roles of the core webhook, hitl, and base modules.
• Universal Architecture Principles: Establishes the three pillars for any Perry addon: HITL safety, non-blocking execution (threading), and Logfire tracing.
• Extensibility Focus: The documentation structure now clearly guides developers on how to build new Perry-compatible addons for any Odoo module (Inventory, HR, etc.).

This ensures the repository communicates that Perry is a scalable framework, not just a set of specific tools.