feat: Thread Message Previews for required messages in main chat flow

[Pratheek555]

As an EmbeddedChat developer

Any user should be able to send a preview of a thread message if they feel it's necessary for everyone to look at.

I need to: Give a checkbox option which enables the user to send a preview of the thread message in main chat flow.

So That: Important discussions in the thread messages do not go unnoticed.

This feature is already implemented in the Rocket.chat repository.

Acceptance Criteria

• [ ] Enabling the checkbox should send a preview of the thread message in the main channel
• [ ] UI for sequential threadPreview and not sequential should be handled.