Add parent_message_id support for threading messages in TypeScript SDK

[sun-runners]

Describe the bug
The current Sendbird Platform SDK for TypeScript does not support parent_message_id, which is required for sending a reply to a message (threading). According to the Sendbird Platform API documentation, the parent_message_id field is essential when creating a reply to a message, but the TypeScript SDK's SendMessageData type does not include this field.

To Reproduce
Steps to reproduce the behavior:

1. Use the SendMessageData type to send a message.
2. Attempt to reply to a message using the parent_message_id.
3. The SendMessageData type does not support the parent_message_id field.

Expected behavior
The SDK should support the parent_message_id field in the SendMessageData type, as described in the Sendbird documentation for threading messages.

Suggested solution
Add the parent_message_id field to the SendMessageData type, allowing users to send reply messages (threaded messages) using the SDK.

Additional context
This feature is necessary for proper implementation of message threading functionality via the TypeScript SDK. It is supported by the Platform API but is missing from the SDK.