Add technical documentation to the docs folder, including architecture, API references, and guides.

[GabrielTrigo]

This pull request introduces comprehensive API reference documentation for key Fougerite scripting systems. The documentation covers the plugin base class, data persistence, permissions, entity wrappers, and event classes, providing detailed usage examples and property/method reference tables for plugin developers.

The most important changes are:

Plugin Base Class and Utilities

• Added a full API reference for BasePlugin, detailing plugin identity, timers (including parallel timers), file I/O (INI/JSON), logging, cross-plugin calls, thread-safe collections, and global shared data, with Python code examples and notes on path safety.

Data Persistence

• Added documentation for the DataStore singleton, explaining thread-safe key-value storage, CRUD operations, Unity type serialization, INI conversion, and practical usage patterns (e.g., home system, kill counter, IP blacklist).

Permission System

• Added a detailed API reference for PermissionSystem, including concepts (groups, wildcards), permission checks, group/player management, querying, reload, temporary revocation, and practical command guard examples.

Entity and Event Wrappers

• Added API documentation for the Entity wrapper, describing identification, position, ownership, health, inventory, linked structures, and destruction, with practical hook usage examples.
• Documented common event classes (e.g., HurtEvent, DeathEvent, GatherEvent, DoorEvent, DecayEvent, CraftingEvent, InventoryModEvent, BanEvent, PlayerApprovalEvent, ConsoleEvent, TimedEvent), including their properties, mutability, and usage in hooks.

[GabrielTrigo]

@dretax , what do you think about this documentation PR?
I originally created this guide for my own use while developing plugins, and it has been very helpful. I figured it might also benefit other developers working on plugins for the project.
Let me know your thoughts!