Adding typescript definition of webrtc-example and added an onErrorCallback hook to detect when webrtc fails

[garbit]

This pull request adds a typescript version of the webrtc example and improves error handling and user feedback to the WebRTC player example, making it more user-friendly and resilient to connection issues. The main changes introduce a UI for displaying errors, a retry mechanism, and propagate session errors from the backend to the frontend.

User-facing improvements:

• Added an error message overlay UI to example.html that displays connection or streaming errors to the user, with a "Retry Connection" button to attempt reconnection. [1] [2] [3] [4] [5]

Error handling and propagation:

• Updated the StreamingSession and VideoPlayer classes in both webrtc-player.js and webrtc-player.ts to accept an errorCallback function, which is called whenever a streaming session error occurs (including disconnections or failures). This callback is used to trigger the UI error overlay. [1] [2] [3] [4]
• Ensured that session termination in StreamingSession invokes the error callback, passing relevant error details to the UI. [1]

Retry mechanism:

• Added logic in example.html to allow the user to retry the connection by clicking the "Retry Connection" button, which stops the current player and attempts to create a new one.

These changes provide clearer feedback and recovery options when streaming issues occur.