feat: Scaffold plugin boilerplate for Webhooks system

[theodesp]

Description

Set up the base structure of the WordPress plugin following best practices. This includes plugin headers, file organization (e.g., src/, includes/, admin/, graphql/, tests/), autoloading (via Composer), activation hooks, and base classes for service loading. It will also register the plugin in WordPress with versioning, basic settings page registration, and prepare for modular development.