Base for SII Modules

This module is a small foundation piece for Chilean localization. It does not add any new screens, fields, or business rules by itself; instead it creates a single menu item named "SII" inside the Settings area of Odoo.

• Where it appears: the new "SII" menu is placed under the Settings menu (the administration menu), so users will see it alongside other configuration options.
• What it does: it only provides the menu container. Other Chilean SII modules can attach their own configuration screens, fields, or actions to this menu.
• Business rules: no checks, computations, default values, restrictions, emails, or scheduled jobs are added by this module.
• Models touched: none. The module depends only on the core base module and does not define or modify any business models.

Because the code is minimal, the practical effect for a user is simply that a new "SII" entry becomes available in Settings, ready to host the configuration of Chilean tax-related features once the companion modules are installed.