Implemented telnet TM option

[mystiker]

Description

This PR introduces support for the Telnet TIMING-MARK (TM) option, enabling synchronization points in the data stream as described in RFC 860. The feature allows the client to handle TIMING-MARK requests while involving the frontend in the acknowledgment process.

How It Works

Server Request:

• When the Telnet server sends a WILL TIMING-MARK, the client does not immediately respond with DO.

Frontend Acknowledgment:

• The client emits a requestTimingMark event to the frontend, signaling the need to acknowledge the TIMING-MARK request.
• he frontend confirms the request through a built-in callback.

Response to Server:

• Once the frontend acknowledges the requestTimingMark, the client sends a DO TIMING-MARK to the Telnet server, completing the negotiation process.
• This approach allows for greater control over TIMING-MARK handling by involving the frontend in the acknowledgment flow, ensuring synchronization requirements are met effectively.

Changes

• Added a requestTimingMark event to notify the frontend of TIMING-MARK requests from the server.
• Implemented a callback mechanism to handle frontend acknowledgment before sending the final DO to the server.

Fixes #129