* Introduces `Connection` class to handle WebSocket connections.
* Defines connection states (connecting, connected, closing, closed) and
exposes getters.
* Implements event listeners for connection state changes and messages.
* Creates `TransactionManager` class to manage transactions over the
connection.
* Enables queuing transactions when the connection is unavailable.
* Binds `TransactionManager` to the `Connection` for message handling.

This commit is part of a major change to support reliable communication
and transaction management.

* Introduces `isSipError`, `isSipHangupEvent`, `isSIPIncomingCallMessage`,
`isSIPCallAcceptedEvent`, and `isSipRingingEvent` functions in `janus.ts` to
identify specific Janus response types for SIP events.
* Adds a `deferredPromise` function in `promise.ts` to create deferred
promises for asynchronous operations.

These functions enhance code readability and provide flexible promise
control for improved message and task management.

* Includes eventemitter3 for event management within the connection class.

This dependency provides a robust event system for the WebSocket connection.

* Introduces `KeepAliveAgent` class to maintain connection health.
* Utilizes `Connection` and `transactionManager` for communication.
* Sends periodic keep-alive transactions (default 10 seconds) to the server.
* Monitors connection state and restarts keep-alive on reconnection.
*  Implements failure handling with a configurable retry mechanism.

This feature ensures the connection remains active and facilitates reliable
communication.

* Introduces `SIPRegistrationAgent` class to handle SIP registration.
* Interacts with `Connection`, `transactionManager`, and `Handler` for
communication.
* Manages registration state (`unregistered`, `registering`, `registered`,
`error`).
* Sends SIP registration transactions using `transactionManager`.
* Handles registration responses, updating state and triggering events.
* Implements error handling and signaling through events.
* Includes a placeholder for `unregister()` for future implementation.

This feature enables automatic SIP registration with error handling and
event notifications.

* Introduces `Call` class to represent SIP calls.
* Manages call states (new, connecting, ringing, active, held, done).
* Handles incoming and outbound call scenarios.
* Provides methods for answering, hanging up, and getting call stats
(placeholder).
* Includes functionality for setting Telnyx call control IDs.

feat: implement call-agent for handling sip call interactions

* Introduces `CallAgent` class for managing SIP call flow.
* Creates and manages `Call` instances for incoming and outgoing calls.
* Interacts with `Connection`, `Peer`, `TransactionManager`, and `Handler`.
* Handles incoming call events (`SIPIncomingCallMessage`).
* Handles SIP hangup events (`JanusSIPHangupEvent`).
* Handles SIP call accepted events (`JanusSIPCallAcceptedEvent`).
* Triggers events (`SwEvent.Notification`) for call updates.
* Implements audio handling for ringtones and ringback tones.

feat: Implement Peer class for WebRTC peer connections

* Introduces `Peer` class to handle WebRTC peer connections for calls.
* Supports creating offer and answer peers based on call options.
* Handles local media stream acquisition with constraints.
* Manages adding media tracks to the peer connection.
* Provides methods for handling ICE trickles and negotiation needed events.
* Implements methods for setting remote SDP and closing the connection.
* Triggers events (`SwEvent.MediaError`) for media acquisition failures.

feat: Implement ICETrickleTransaction for sending ICE candidates

* Introduces `ICETrickleTransaction` to send ICE candidates to Janus.
* Constructs a Janus `trickle` request with candidate information.
* Handles success and error responses from Janus on message received.

feat: Implement SIPAnswerTransaction for sending SIP answer

* Introduces `SIPAnswerTransaction` for sending SIP answer messages.
* Constructs a Janus `message` request with answer SDP and other details.
* Handles success (`isSIPCallAcceptedEvent`) and error (`isSipError`)
responses.
* Resolves with call ID on successful SIP answer reception.

feat: Implement SIPCallTransaction for initiating SIP calls

* Introduces `SIPCallTransaction` for initiating SIP calls via Janus.
* Constructs a Janus `message` request with call details, URI, and SDP.
* Handles success (`isSipRingingEvent`) and error (`isSipError`) responses.
* Resolves with call ID, Telnyx IDs, on successful SIP call initiation.

feat: Implement SIPHangupTransaction for terminating SIP calls

* Introduces `SIPHangupTransaction` for sending SIP hangup messages.
* Constructs a Janus `message` request with the hangup request.
* Handles success (`janus === ack`) and error (`janus === error`) responses.
* Resolves with `true` on successful SIP hangup.

* Introduces JanusClient class as the central component for SIP calls.
* Manages connection to Janus server, plugin attachment, and SIP
registration.
* Handles call creation and management through CallAgent.
* Provides methods for connecting, making calls, getting calls, and setting
remote media element.
* Includes event handling for listening to call events.
* Implements stubs for enabling/disabling webcam and disconnection (to be
completed).

BREAKING CHANGE: Introduces a new class for core functionality, potentially
affecting code organization and usage.