Replace RTCPeerConnection.addStream() with .addTrack()

[RTCPeerConnection.addStream()](https://github.com/takahirox/nes-rust/blob/7f0157fd1caea8f51d33fbeadb5a4a5cf321228b/js/network/WebRTCClient.js#L484-L485) is deprecated.

https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/addStream

We should use `.addTrack()` instead.