Support for System Messages / Custom Message Types

[trongvinh2804]

Currently, it is not possible to display system messages (such as "User joined the group", "User left the group", or other system notifications) with a distinct style in the chat. The MessageType enum is fixed and does not allow for custom or system message types, making it difficult to implement real-world chat features that require system notifications.

I would like the package to support system messages or custom message types. For example:

• Add a system value to the MessageType enum, or
• Allow developers to define custom message types and provide custom UI rendering for them, or
• Provide an official mechanism for displaying system notifications in the chat view (centered, with different style, etc.)

I have tried to work around this by using a special user (e.g., "SYSTEM") or by using the "custom" message type, but this approach is limited and does not allow for a truly distinct UI or message handling. It also leads to type conflicts when using chatview_connect and chatview together with custom modifications.

This feature would be very useful for many real-world chat applications, such as group join/leave notifications, admin announcements, or other system events.
Thank you for considering this request!