docs: add scripting events guide

[Kheartz]

Summary

• Add a comprehensive guide explaining the HogwartsMP event system.
• Document event subscriptions, scopes, client/server communication, and payload handling.
• Catalog core/native server events and native client events.
• Document spellCast, armed combat events, feature-specific events, and web-view lifecycle events.
• Explain client-event trust boundaries and server-side validation requirements.
• Correct the overview example now that network payloads arrive as parsed values.