Add metadata to ChatMessage

[aledeloss]

We need to add metada to messages, so we can use it in the frontend for custom styling, for example. Is it possible?
If not, do you think that it is feasible? I think that an optional metadata attribute in ChatMessage would work.
Thanks!

[supersnager]

@aledeloss Could you try the version from this branch https://github.com/chatscope/use-chat/tree/v4.0.0-alpha.9 ?
https://www.npmjs.com/package/@chatscope/use-chat/v/4.0.0-alpha.9
There is a generic parameter for additional data property

use-chat/src/ChatMessage.ts

Line 63 in c9977f2

export class ChatMessage<T extends MessageContentType, D = undefined> {

If it works, I can release a new major version based on the alpha branch.

[singpolyma]

that version working well for me